Concentrated solar power generation using solar receivers

ABSTRACT

Inventive concentrated solar power systems using solar receivers, and related devices and methods, are generally described. Low pressure solar receivers are provided that function to convert solar radiation energy to thermal energy of a working fluid, e.g., a working fluid of a power generation or thermal storage system. In some embodiments, low pressure solar receivers are provided herein that are useful in conjunction with gas turbine based power generation systems.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/361,074, filed Mar. 21, 2019, now U.S. Pat. No. 11,242,843 issued onFeb. 8, 2022, and entitled “Concentrated Solar Power Generation UsingSolar Receivers,” which is a continuation of U.S. patent applicationSer. No. 15/667,222, filed Aug. 2, 2017, now U.S. Pat. No. 10,280,903issued on May 7, 2019, and entitled “Concentrated Solar Power GenerationUsing Solar Receivers,” which is a continuation of U.S. patentapplication Ser. No. 13/823,013, filed Jul. 29, 2013, now U.S. Pat. No.9,726,155 issued on Aug. 8, 2017, and entitled “Concentrated Solar PowerGeneration Using Solar Receivers,” which is a national stage ofInternational Patent Application No. PCT/US2011/052051, filed Sep. 16,2011, and entitled “Concentrated Solar Power Generation Using SolarReceivers,” which claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 61/383,561, filed Sep. 16, 2010,and entitled “Brayton Cycle Concentrated Solar Power Generation Using aLow Pressure Solar Receiver;” U.S. Provisional Patent Application Ser.No. 61/383,570, filed Sep. 16, 2010, and entitled “Heat Recovery in aConcentrated Solar Power Generation System;” U.S. Provisional PatentApplication Ser. No. 61/383,608, filed Sep. 16, 2010, and entitled “LowPressure Solar Receivers for Concentrated Solar Power Generation;” U.S.Provisional Patent Application Ser. No. 61/383,619, filed Sep. 16, 2010,and entitled “Secondary Concentrators for Concentrated Solar PowerGeneration;” U.S. Provisional Patent Application Ser. No. 61/383,631,filed Sep. 16, 2010, and entitled “Solar Power Generation System andMethod with Modularized Components;” and U.S. Provisional PatentApplication Ser. No. 61/383,598, filed Sep. 16, 2010, and entitled“Concentrated Solar Power Generation Using Pressurized Solar ReceiversComprising Single Crystal Nickel;” each of which is incorporated hereinby reference in its entirety for all purposes.

GOVERNMENT SUPPORT

This invention was made with government support under grantDE-EE-0003587 awarded by the Department of Energy. The government hascertain rights in the invention.

FIELD OF INVENTION

Systems, devices, and methods related to concentrated solar powergeneration using solar receivers are generally described.

BACKGROUND

Mounting concerns over the effect of greenhouse gases on global climatehave stimulated research focused on limiting greenhouse gas emissions.Solar power generation is particularly appealing because substantiallyno greenhouse gases are produced at the power generation source.

Concentrated solar power (CSP) generation using solar receivers is knownin the art. Briefly, concentrated solar power systems use lenses,mirrors, or other elements to focus sunlight incident on a relativelylarge area onto a small area called a solar receiver. The concentratedsunlight can be used to heat a fluid within the solar receiver. Thefluid heated within the solar receiver can be used to drive a turbine togenerate power.

SUMMARY OF THE INVENTION

Inventive concentrated solar power systems using solar receivers, andrelated devices and methods, are generally described. In someembodiments, the concentrated solar power systems include a low pressuresolar receiver. In addition, inventive heat recovery systems and methodsfor use in concentrated solar power generation systems using solarreceivers are generally described.

Inventive solar receivers for use in concentrated solar power systems,and related systems, devices and methods, are also generally described.In some embodiments, low pressure solar receivers are provided thatfunction to convert solar radiation energy to thermal energy of aworking fluid, e.g., a working fluid of a power generation or thermalstorage system. In some embodiments, the low pressure solar receivershave lower cost of production and significantly larger collectioncapacity than typical currently available solar receivers.

Inventive concentrators for use in concentrated solar power systems, andrelated systems, devices and methods, are also generally described. Insome embodiments, the concentrators include integrated cooling systemsto maintain components of the concentrator at predetermined and/ordesired temperatures. In other embodiments, methods for producingconcentrators having integrated cooling systems to maintain componentsparts at predetermined and/or desired temperatures are provided.

Inventive systems and methods related to solar power generation usingmodular components are also generally described.

Inventive concentrated solar power systems using pressurized solarreceivers, and related devices and methods, are also generallydescribed. In some embodiments, the concentrated solar power systemsinclude a solar receiver comprising single crystal nickel.

The subject matter of the present invention involves, in some cases,interrelated products, alternative solutions to a particular problem,and/or a plurality of different uses of one or more systems and/orarticles.

In some embodiments of invention, power generation systems are provided.In some embodiments, the power generation systems comprise a solarreceiver constructed and arranged to heat a first gas at a pressure ofless than or equal to 2 atmospheres; a heat exchanger (e.g., a hightemperature heat exchanger) fluidically connected to the solar receiver,constructed and arranged to simultaneously contain the first gas and asecond gas at a pressure of above 2 atmospheres and to transfer thermalenergy from the first gas to a second gas; and a gas turbine fluidicallyconnected to the solar receiver, constructed and arranged to generatepower using the second gas.

In further embodiments of the invention, methods of generating power areprovided. In some embodiments, the methods comprise heating a first gasat a pressure of less than or equal to 2 atmospheres in a solarreceiver; transferring thermal energy from the first gas to a second gasat a pressure of above 2 atmospheres using a heat exchanger (e.g., ahigh temperature heat exchanger) fluidically connected to the solarreceiver and configured to simultaneously contain the first gas and thesecond gas; and generating power from the second gas using a gas turbinefluidically connected to the solar receiver.

In some embodiments of the foregoing systems or methods, the heatexchanger (e.g., high temperature heat exchanger) is a ceramic heatexchanger. In some embodiments of the foregoing systems or methods, theheat exchanger is a metallic heat exchanger. In some embodiments of theforegoing systems or methods, an exhaust stream of the gas turbine isdirectly fluidically connected to the solar receiver. In someembodiments of the foregoing systems or methods, an exhaust stream ofthe solar receiver is directly fluidically connected to the heatexchanger.

In some embodiments of the foregoing power generation systems or methodsof generating power, the pressure of the first gas is less than or equalto 2 atmospheres, less than about 1.5 atmospheres, less than about 1.25atmospheres or is less than about 1.1 atmospheres, between about 0.9 andabout 2 atmospheres, between about 0.9 and about 1.5 atmospheres,between about 0.9 and about 1.25 atmospheres, or between about 0.9 andabout 1.1 atmospheres. In some embodiments of the foregoing systems andmethods, the pressure of the second gas is above 2 atmospheres, at leastabout 2.1 atmospheres, at least about 2.25 atmospheres, at least about2.5 atmospheres, at least about 3 atmospheres, at least about 4atmospheres, at least about 5 atmospheres, at least about 10atmospheres, at least about 15 atmospheres, and, in some embodiments, upto 25 atmospheres or up to 50 atmospheres.

In some embodiments of the foregoing power generation systems or methodsof generating power, the second gas is transported to the gas turbineafter being heated by the heat exchanger. In some embodiments of theforegoing systems or methods, a compressor fluidically connected to theheat exchanger is constructed and arranged to compress a gas to producethe second gas. In some embodiments of the foregoing systems or methods,an exhaust stream of the compressor is directly fluidically connected tothe heat exchanger. In some embodiments of the foregoing systems ormethods, the gas compressed by the compressor comprises ambient air.

In some embodiments, power generation systems are provided that comprisea solar receiver constructed and arranged to heat a first gas; a heatexchange system comprising first and second heat exchange unitsfluidically connected to the solar receiver, constructed and arranged totransfer thermal energy from the first gas to a second gas; and a gasturbine fluidically connected to the solar receiver, constructed andarranged to generate power using the second gas.

In some embodiments, methods of generating power are provided thatcomprise heating a first gas within a solar receiver; transferringthermal energy from the first gas to a second gas within a heat exchangesystem comprising first and second heat exchange units fluidicallyconnected to the solar receiver; and generating power using the secondgas using a gas turbine fluidically connected to the solar receiver.

In some embodiments of the foregoing power generation systems or methodsof generating power, the heat exchange system comprises at least onerotary heat exchanger. In certain embodiments, the heat exchange systemcomprises at least one ceramic rotary heat exchanger. In certainembodiments, the heat exchange system comprises at least one metallicheat exchanger.

In some embodiments of the foregoing power generation systems or methodsof generating power, the gas from the solar receiver is transported to ahigh temperature heat exchanger, and subsequently transported to a lowertemperature heat exchanger. In some embodiments of the foregoing systemsor methods, an exhaust stream of the gas turbine is directly fluidicallyconnected to the solar receiver.

In some embodiments of the foregoing power generation systems or methodsof generating power, the pressure of the first gas is less than or equalto 2 atmospheres, less than about 1.5 atmospheres less than about 1.25atmospheres, or less than about 1.1 atmospheres between about 0.9 andabout 2 atmospheres, between about 0.9 and about 1.5 atmospheres,between about 0.9 and about 1.25 atmospheres, or between about 0.9 andabout 1.1 atmospheres. In some embodiments of the foregoing systems ormethods, the pressure of the second gas is above 2 atmospheres, at leastabout 2.1 atmospheres, at least about 2.25 atmospheres, at least about2.5 atmospheres, at least about 3 atmospheres, at least about 4atmospheres, or at least about 5 atmospheres, at least about 10atmospheres, at least about 15 atmospheres, and, in some embodiments, upto 25 atmospheres or up to 50 atmospheres.

In some embodiments of the foregoing power generation systems or methodsof generating power, the second gas is transported to the gas turbineafter being heated by the heat exchange system. In some embodiments ofthe foregoing systems or methods, a compressor fluidically connected tothe heat exchange system is constructed and arranged to compress a gasto produce the second gas. In some embodiments of the foregoing systemsor methods, an exhaust stream of the compressor is directly fluidicallyconnected to the heat exchange system. In some embodiments of theforegoing systems or methods, the gas compressed by the compressorcomprises ambient air.

In some aspects of the invention, systems are provided that comprise asolar receiver constructed and arranged to heat a gas at a pressure ofless than or equal to 2 atmospheres; a thermal storage systemfluidically connected to the solar receiver; and a heat exchange systemfluidically connected to the solar receiver. In some embodiments, theheat exchange system is constructed and arranged to transfer thermalenergy from the gas heated by the solar receiver to a second gas. Insome embodiments, the system is constructed and arranged such that afirst portion of the gas heated by the solar receiver can be transportedto the low pressure thermal storage system and a second portion of thegas heated by the solar receiver can be transported to the heat exchangesystem. In some embodiments, the thermal storage system is constructedand arranged to be operated (e.g., heated with a fluid) at a pressure ofless than or equal to 2 atmospheres.

In some aspects of the invention, methods are provided that compriseheating a gas at a pressure of less than or equal to 2 atmosphereswithin a solar receiver; transporting a first portion of the gas fromthe solar receiver to a thermal storage system fluidically connected tothe solar receiver; and transporting a second portion of the gas fromthe solar receiver to a heat exchange system fluidically connected tothe solar receiver. In some embodiments, the heat exchange system isconstructed and arranged to transfer thermal energy from the gas heatedby the solar receiver to a second gas. In some embodiments, the thermalstorage system is constructed and arranged to be operated at a pressureof less than or equal to 2 atmospheres

In some embodiments of the foregoing systems or methods, substantiallyall of the gas from the solar receiver is transported to the thermalstorage system over a first period of time, and substantially all of thegas from the solar receiver is transported to the heat exchange systemover a second period of time that does not overlap with the first periodof time.

In some embodiments of the foregoing systems or methods, a first portionof the gas from the solar receiver is transported to the thermal storagesystem over a first period of time, and a second portion of the gas fromthe solar receiver is transported to the heat exchange system over thefirst period of time.

In some embodiments of the foregoing systems or methods, the thermalstorage system is constructed and arranged to be operated at a pressureof less than or equal to 2 atmospheres, less than about 1.5 atmospheres,less than about 1.25 atmospheres, or less than about 1.1 atmospheresbetween about 0.9 and about 2 atmospheres, between about 0.9 and about1.5 atmospheres, between about 0.9 and about 1.25 atmospheres, orbetween about 0.9 and about 1.1 atmospheres.

In some embodiments of the foregoing systems or methods, the thermalstorage system comprises at least one thermal storage tank. In someembodiments of the foregoing systems or methods, the thermal storagesystem comprises fill media. In certain embodiments, the fill mediacomprises aluminum oxide, iron oxide, silicon oxide, and/or magnesiumoxide, or other media. In certain embodiments, the fill media comprisespellets (e.g., spheres or other configurations described in more detailbelow). In some embodiments, at least about 50% of the pellets havemaximum cross-sectional diameters of less than about 100 cm. In someembodiments, the thermal storage system is located within the towerstructure of a power tower.

In some embodiments of the foregoing systems or methods, the pressure ofthe gas within the solar receiver is less than or equal to 2atmospheres, less than about 1.5 atmospheres, less than about 1.25atmospheres or less than about 1.1 atmospheres between about 0.9 andabout 2 atmospheres, between about 0.9 and about 1.5 atmospheres,between about 0.9 and about 1.25 atmospheres, or between about 0.9 andabout 1.1 atmospheres.

In some embodiments, the foregoing systems or methods further comprise agas turbine constructed and arranged to produce power using the secondgas, for example, as part of a Brayton cycle.

In some embodiments of the invention, power generation systems areprovided that comprise a solar receiver constructed and arranged to heata gas at a pressure of less than or equal to 2 atmospheres; a gasturbine fluidically connected to the solar receiver such that all or aportion of the gas heated by the solar receiver includes the exhaust ofthe gas turbine; and a blower fluidically connected to the solarreceiver such that a portion of the gas heated by the solar receiverincludes the exhaust of the blower.

In some embodiments of the invention, methods of generating power areprovided that comprise producing power using a first gas at a pressureof greater than 2 atmospheres within a gas turbine; transporting atleast a portion of the exhaust stream of the gas turbine to a solarreceiver; transporting a second gas from a blower to the solar receiver;and heating the first and second gases within the solar receiver. Incertain embodiments, the gas transported from the gas turbine to thesolar receiver has a pressure of less than or equal to 2 atmospheres.

In some embodiments of the foregoing power generation systems or methodsof generating power, the exhaust of the gas turbine is not substantiallyfurther compressed before being transported to the solar receiver.

In some embodiments of the foregoing power generation systems or methodsof generating power, a controller is constructed and arranged to adjustthe flow rate of the second gas transported from the blower to the solarreceiver based at least in part on a condition of the gas transportedfrom the gas turbine to the solar receiver. In some embodiments, thecondition is the temperature of the gas transported from the gas turbineto the solar receiver. In some embodiments, the condition is thepressure of the gas transported from the gas turbine to the solarreceiver. In some embodiments, the condition is the flow rate of the gastransported from the gas turbine to the solar receiver.

In some embodiments of the foregoing power generation systems or methodsof generating power, the first gas is at a pressure of above 2atmospheres, at least about 2.1 atmospheres, at least about 2.25atmospheres, at least about 2.5 atmospheres, at least about 3atmospheres, at least about 4 atmospheres, at least about 5 atmospheres,at least about 10 atmospheres, at least about 15 atmospheres, and, insome embodiments, up to 25 atmospheres or up to 50 atmospheres.

In some embodiments of the foregoing power generation systems or methodsof generating power, the gas transported from the gas turbine to thesolar receiver has a pressure of less than or equal to 2 atmospheres,less than about 1.5 atmospheres, less than about 1.25 atmospheres, orless than about 1.1 atmospheres, between about 0.9 and about 2atmospheres, between about 0.9 and about 1.5 atmospheres, between about0.9 and about 1.25 atmospheres, or between about 0.9 and about 1.1atmospheres. In some embodiments, the gas turbine is directlyfluidically connected to the solar receiver. In some embodiments, theblower is directly fluidically connected to the solar receiver. In someembodiments of the invention, heat recovery systems are provided. Insome embodiments, the systems comprise a solar receiver constructed andarranged to heat a first, relatively low pressure fluid; a first heatexchanger fluidically connected to the solar receiver, constructed andarranged to transfer energy from the first, relatively low pressurefluid to a second, relatively high pressure fluid; and a second heatexchanger fluidically connected to the first heat exchanger, constructedand arranged to transfer energy from the first, relatively low pressurefluid to a third fluid.

In some embodiments of the foregoing heat recovery systems, the first,relatively low pressure fluid is at a pressure of less than or equal to2 atm, less than about 1.5 atm, or less than about 1.1 atm. In someembodiments of the foregoing systems, the second, relatively highpressure fluid is at a pressure above 2 atm, at least about 3 atm, or atleast about 5 atm.

In some embodiments of the foregoing heat recovery systems, the thirdfluid is used as part of a Rankine cycle. In some embodiments of theforegoing systems, the third fluid is used to provide heat to anabsorption chiller. In some embodiments of the foregoing systems, thethird fluid is used to provide heat to a liquid. In some embodiments ofthe foregoing systems, the heated liquid is used for space heatingpurposes.

In some embodiments of the foregoing heat recovery systems, the firstheat exchanger is fluidically connected to a turbine. In certainembodiments, the turbine is a gas turbine, which can be used, forexample, as part of a Brayton cycle.

In some embodiments of the invention, solar receivers are provided. Insome embodiments, the solar receivers comprise a low pressure fluidchamber comprising a fluid inlet, a fluid outlet, and an opening forreceiving concentrated solar radiation; a solar absorber housed withinthe low pressure fluid chamber; and a transparent object that defines atleast a portion of a wall of the low pressure fluid chamber, whereinconcentrated solar radiation received through the opening passes throughthe transparent object into the low pressure fluid chamber and impingesupon the solar absorber.

In some embodiments of the foregoing solar receivers, the low pressurefluid chamber defines a fluid flow path from the fluid inlet to thefluid outlet. In certain embodiments, between the fluid inlet and thefluid outlet, the fluid flow path extends across at least a portion ofthe transparent object. In certain embodiments, the fluid flow pathextends through one or more passages within the solar absorber.

In some embodiments of the foregoing solar receivers, the transparentobject has a parabolic shape. In certain embodiments, the concave faceof the parabolic shape is directed toward the opening. In certainembodiments, the transparent object has a radius of curvature of 1 footto 50 feet. In certain embodiments, the transparent object has a radiusof curvature of 1 foot to 10 feet. In certain embodiments, thetransparent object has a radius of curvature of 5 feet to 20 feet. Incertain embodiments, the transparent object has a radius of curvature ofapproximately 15 feet. In one embodiment, the transparent object has aradius of curvature of 1 foot of 5 feet. In certain embodiments, thetransparent object has a planar disc shape. In some embodiments, thetransparent object has a diameter in a range of 1 meter to 5 meters or 2meters to 4 meters or 1 meter to 2 meters. In certain embodiments, thetransparent object has a thickness in a range of 0.5 inch to 4 inches or0.5 inch to 1 inch or 0.5 inch to 2 inch.

In some embodiments of the foregoing solar receivers, the maximumallowable working pressure of the low pressure fluid chamber is equal toor less than 2 atm, less than 2 atm, less than 1.5 atm, or less than 1.1atm. In some embodiments of the foregoing solar receivers, the maximumallowable working pressure of the low pressure fluid chamber is up to2×, up to 3×, up to 4×, up to 5×, up to 10× its operating pressure.

In some embodiments of the foregoing solar receivers, the low pressurefluid chamber defines a recess within which an outer rim of thetransparent object expandably fits, the recess being adjacent to theopening. In some embodiments, the solar receivers further comprise aseal element positioned between the outer rim of the transparent objectand an interface defined by the recess on the low pressure fluidchamber. In certain embodiments, the seal element is a room temperaturevulcanizing (RTV) silicone or ceramic fiber rope.

In some embodiments of the foregoing solar receivers, the transparentobject is quartz or silica glass. In some embodiments of the foregoingsolar receivers, the solar absorber is a material selected from a groupconsisting of metals, stainless steels, ceramics, heat-resistant castalloys, high-temperature metallic materials, refractory materials,thoria-dispersed alloys, graphite, and carbon-fiber-reinforcedcarbon-based materials.

In some embodiments of the foregoing solar receivers, the solar absorberis a ceramic. In certain embodiments, the ceramic is a glass ceramic. Incertain embodiments, the ceramic is silicon carbide or silicon nitride.In one embodiment, the ceramic is silicon oxide.

In some embodiments of the foregoing solar receivers, the solar absorberis a wire mesh. In some embodiments of the foregoing solar receivers,the solar absorber has a honeycomb configuration. In some embodiments ofthe foregoing solar receivers, the solar absorber comprises a ceramicfoam. In some embodiments of the foregoing solar receivers, the solarabsorber comprises a black surface coating. In some embodiments, thesolar absorber comprises a plurality of segments. In some embodiments,the solar absorber comprises a plurality of pie-shaped segments. Incertain embodiments, each of the plurality of segments has a honeycombconfiguration. In some certain embodiments, the solar receiver each ofthe plurality of segments comprises a ceramic foam. In some embodiments,the solar absorber has a concave face directed toward the opening. Insome embodiments, the solar receiver absorber has a substantially planarshape.

In some embodiments, the foregoing solar receivers further comprise asecondary concentrator connected to the low pressure fluid chamber atthe opening. In some embodiments, the secondary concentrator comprises aplurality of reflective panels arranged such that incident solarradiation impinging the reflective panels is reflected toward thetransparent object. In certain embodiments, the plurality of reflectivepanels are arranged to form a parabolic shape. In certain embodiments,the plurality of reflective panels are arranged to form a plurality ofconical rings that are arranged in a series such that each successivering in the series has a larger diameter, the largest diameter conicalring being furthest from the opening. In certain embodiments, theplurality of reflective panels consists of forty-eight interconnectedpanels. In one embodiment, each conical ring consists of twelvereflective panels. In some embodiments, each reflective panel has aplanar rectangular shape. In certain embodiments, the plurality ofreflective panels consists of four interconnected reflective panels. Insome embodiments, each reflective panel has a conical ring shape. Insome embodiments, each reflective panel comprises an inner reflectivesurface, an outer surface and a cooling fluid passage. In certainembodiments, each reflective panel is bonded to a casing such that acavity is formed between the casing and the outer surface, wherein thecavity is the cooling fluid passage. In some embodiments, the casinginterfaces with a plurality of raised portions on the outer surface ofthe reflective panel. In certain embodiments, the casing is bonded tothe reflective panel by a metal-to-metal bond. In certain embodiments,the metal-to-metal bond is a braze weld, a resistance weld or acompression weld. In certain embodiments, the raised portions are knurlsor embossments.

In some embodiments of the foregoing solar receivers, the fluid inlet isfluidically connected with a gas turbine exhaust outlet. In someembodiments of the foregoing solar receivers, the fluid outlet isfluidically connected with a gas turbine compressor inlet or a thermalstorage system. In some embodiments of the foregoing solar receivers,the fluid outlet is fluidically connected with a regenerator unit. Incertain embodiments, the regenerator unit is a rotary regenerator unit.

In some aspects of the invention, concentrators for solar receivers areprovided. In some embodiments, the concentrators comprise a supportstructure defining an inlet for receiving solar radiation and an outletfor discharging concentrated solar radiation; and a plurality ofreflective panels, each reflective panel comprising one or more fluidpassages, wherein the plurality of reflective panels are connected tothe support structure and arranged such that incident solar radiationimpinging the reflective panels is reflected toward the outlet.

In some embodiments of the concentrators, the plurality of reflectivepanels are arranged to form a parabolic, semi-circular, orsemi-elliptical shape. In some embodiments of the concentrators, theplurality of reflective panels are arranged to form a plurality ofconical rings arranged in a series. In some embodiments of theconcentrators, the plurality of reflective panels consists of 2 to 72reflective panels. In some embodiments of the concentrators, theplurality of reflective panels consists of 48 reflective panels. In someembodiments of the concentrators, each conical ring comprises 1 to 24reflective panels. In one embodiment, each conical ring comprises 12reflective panels.

In one embodiment of the concentrators, each reflective panel has aplanar shape. In certain embodiments, each reflective panel has apolyhedron shape or disc shape. In some embodiments, the plurality ofreflective panels consists of four reflective panels, wherein eachreflective panel has a conical ring shape.

In some embodiments of the concentrators, each reflective panel isbonded to a casing such that a cavity is formed between the casing andan outer surface of the reflective panel, wherein the cavity is acooling fluid passage. In certain embodiments, the casing interfaceswith a one or more raised portions on the outer surface of thereflective panel. In certain embodiments, the casing is bonded to thereflective panel by a metal-to-metal bond. In some embodiments, themetal-to-metal bond is a braze weld, a resistance weld or a compressionweld. In certain embodiments, the raised portions are knurls orembossments. In some embodiments, the casing is aluminum. In someembodiments, the reflective panel comprises a metal, a polymer, a glass,or a combination thereof. In some embodiments, the reflective panelcomprises aluminum, silver, or a combination thereof.

In some aspects of the invention, methods for producing a solar receiverare provided. In some embodiments, the methods comprise obtaining asolar receiver comprising an opening for receiving solar radiation and asolar absorber for absorbing incident solar radiation and transferringthermal energy to a working fluid; and mounting any of the foregoingconcentrators on the solar receiver such that the outlet of theconcentrator is operably positioned within, or adjacent to, the openingof the solar receiver.

In some aspects of the invention, systems are provided for cooling aconcentrator for a solar receiver. In some embodiments, the systemscomprise a reservoir comprising a working fluid; any appropriateconcentrator disclosed herein; one or more conduits fluidicallyconnecting the reservoir with one or more cooling passages of eachreflective panel of the concentrator; and a pump configured forcirculating a working fluid from the reservoir through the one or moreconduits.

In some embodiments, the systems further comprise a heat exchangerdownstream of the concentrator configured for removing heat from theworking fluid. In certain embodiments, the heat exchanger is a coolingtower. In certain embodiments, the heat exchanger is a shell-and-tubeheat exchanger or a plate-type heat exchanger. In some embodiments, theworking fluid circulates back to the reservoir after leaving the heatexchanger. In certain embodiments, the working fluid is an antifreezesolution. In certain embodiments, the working fluid is a mixture ofwater and glycol. In some embodiments, the working fluid is a 50:50mixture of water and glycol. In certain embodiments, the glycol isethylene glycol or propylene glycol.

In further aspects of the invention, methods are provided for modifyinga reflective panel for a concentrator. In some embodiments, the methodscomprise obtaining a reflective panel having a inner reflective surfaceand an outer surface; creating one or more raised portions on the outersurface of the reflective panel; overlaying a casing on the outersurface of the reflective panel such that the casing contacts the one ormore raised portions; and bonding the casing to the reflective panel tocreate a cavity between the casing and the outer surface of thereflective panel.

In further aspects of the invention, methods are provided for producinga concentrator. In some embodiments, the methods comprise obtaining aplurality of reflective panels, each reflective panel having a innerreflective surface and an outer surface; obtaining a support structuredefining an inlet for receiving solar radiation and an outlet fordischarging concentrated solar radiation; and assembling the pluralityof reflective panels such that each reflective panel is connected to thesupport structure and arranged such that incident solar radiationimpinging the reflective panels is reflected toward the outlet. In someembodiments, the methods further comprise creating one or more raisedportions on the outer surface of each reflective panel; overlaying acasing on the outer surface of each reflective panel such that thecasing contacts the one or more raised portions; and bonding the casingto the reflective panel to create a cavity between the casing and theouter surface of the reflective panel. In some embodiments, the methodsfurther comprise fluidically connecting one or more conduits to thecavity of each reflective panel. In some embodiments, the raisedportions are knurls or embossments. In some embodiments, the casing is ametal sheet. In some embodiments, the casing is an aluminum sheet. Insome embodiments, bonding comprises creating a metal-to-metal bondbetween the casing and the reflective panel. In some embodiments, themetal-to-metal bond is a laser weld, a braze weld, a resistance weld ora compression weld.

Inventive concentrated solar power systems using solar receivers, andrelated devices and methods, are also generally described. In someembodiments, the concentrated solar power system or method includes oneor more modularized components. For example, in one embodiment,turbines, concentrators, recuperators, receivers and/or other componentsmay be integrated into a single unit. The single unit may be assembledat a factory or other location away from the operation site and thenshipped to the operation site, e.g., by truck over an interstate highwaysystem. Once at the operation site, the single unit may be incorporatedinto a power generation system, e.g., by placement of the unit on atower. Since many components of the system may be manufactured andassembled together in a factory or other similar setting away from theoperation site, and then shipped to the operation site after testing,assembly costs and complexity may be reduced.

In another aspect of the invention, a receiver, concentrator, energystorage tank(s), recuperator(s) and/or turbine(s) for a solar powergeneration system may be elevated from ground level, e.g., installed atthe top of a tower. Such an arrangement may allow the recuperator(s)and/or turbine(s) to be located more closely to the receiver, reducingheat loss and/or other costs resulting from having the recuperators andturbines located a further distance away from the receiver. As is known,the receiver in heliostat-based solar power generation systems istypically mounted on a tower or otherwise elevated above the ground onwhich the heliostats are arranged so that the heliostats can operatemore efficiently in directing sunlight to the receiver. In prior solargeneration systems, recuperators and turbines that receive heated fluidfrom the receiver are located at ground level, usually because thereceiver, recuperator and turbine assemblies are relatively heavy—tooheavy to be safely or efficiently mounted together on a tower. Forexample, prior receiver arrangements operate at relatively highpressure, e.g., 4-14 atmospheres and more, and thus must be made ofthick and heavy material to withstand the pressures. As a result, thereceiver itself typically requires a relatively large and robust towerstructure. To include the recuperator, turbine and other components onthe tower would require that the tower be made so strong and large as tooffset any gain that might be realized in locating the components moreclosely together. With the recuperator and/or turbine assemblies locatedon the ground, heated fluid from the receiver must be directed from thereceiver at the top of a tower to the ground where the recuperators andturbines are located. Transporting fluid up and down the tower increasesthe size and weight of the system further, e.g., tubes conducting hightemperature/high pressure fluid up and down the tower must be madesufficiently thick or otherwise arranged to operate safely and reduceheat loss.

As is described below, aspects of the invention allow for relatively lowpressure operation of the solar power generator (at least at thereceiver), which may help to reduce the size and/or weight of systemcomponents. That is, the reduced pressures may require less material tosafely contain fluid pressure (e.g., allow for thinner tube, housing andtank wall thicknesses), reducing the weight of various systemcomponents, and particularly the weight of the receiver. This reducedweight may permit the inclusion of other system components on a tower inaddition to the receiver, e.g., turbines, recuperators, energy storagetanks and other components may be mounted together on a tower. This maynot only reduce the footprint of the system on the ground, but also helpto reduce system construction and assembly costs. For example, thesmaller size and weight components may be assembled together into one ormore units that can be shipped from a factory (e.g., by truck orrailroad car) and then assembled on the tower at the operation site. Inone embodiment, all of the receiver, concentrator, energy storagetank(s), recuperator(s) and turbine(s) for a solar power generationsystem may be mounted to a tower. Thus, the power generation system,aside from heliostats, power transmission components and associatedcontrol systems, may be completely contained on a tower in someembodiments. In other embodiments, a receiver, concentrator,recuperator(s) and turbine(s) may be mounted on a tower, with one ormore energy storage tanks located at ground level, or inside of thetower base.

In another embodiment, the receiver and concentrator may be made as asingle modular unit, and the turbines may be made as a separate, singlemodular unit. The receiver/concentrator and turbine units may beassembled and mounted together on a tower. Constructing portions of thepower generation system as discrete modular units may also permit eachof the modules to be fully tested for satisfactory operation prior toshipping the modular units from a factory to a work site. This mayreduce the number or extent of system testing at the work site since theoperation of each of the modular units may be ensured prior to assemblyat the operation site.

In some aspects of the invention solar power systems are provided. Insome embodiments, the systems comprise a first solar receiverconstructed and arranged to heat a gas at a pressure of less than orequal to 2 atm, the first solar receiver fluidically connected to athermal storage system; and a second solar receiver constructed andarranged to heat a gas at a pressure of above 2 atm, the second solarreceiver fluidically connected to the thermal storage system.

In some aspects of the invention, methods are provided that compriseheating a first gas at a pressure of less than or equal to 2 atm withina first solar receiver fluidically connected to a thermal storagesystem; and heating a second gas at a pressure of above 2 atm within asecond solar receiver fluidically connected to the thermal storagesystem.

In some embodiments of the systems or methods, the first solar receiveris directly fluidically connected to the thermal storage system. In someembodiments of the systems or methods, the second solar receiver isdirectly fluidically connected to the thermal storage system. In someembodiments of the systems or methods, a first portion of the thermalstorage system is constructed and arranged to be operated at a pressureof above 2 atm, and a second portion of the thermal storage system isconstructed and arranged to be operated at a pressure of less than orequal to 2 atm. In some embodiments of the systems or methods, thethermal storage system is fluidically connected to a gas turbine.

In further aspects of the invention, solar receivers are provided. Insome embodiments, the solar receivers comprise an insulating casingcomprising an opening for receiving concentrated solar radiation; and ahigh pressure solar absorber housed within the insulating casing. Insome embodiments, the high pressure solar absorber comprises a fluidinlet, a fluid outlet, and a heat exchanger fluidically connected withthe fluid inlet and the fluid outlet. In some embodiments, the highpressure solar absorber has a maximum allowable working pressure inexcess of 2 atmospheres. In some embodiments, the high pressure solarabsorber is designed and configured to operate at a temperature of 800°C. to 1500° C. or 800° C. to 2500° C. In some embodiments, the highpressure solar absorber is designed and configured to operate at atemperature of equal to or above 800° C.

In some embodiments, the solar receivers further comprise a transparentobject positioned adjacent to the opening. In some embodiments, thetransparent object reflects light in the infrared range. In someembodiments, the transparent object comprises an anti-radiationreflection coating on an inside surface that limits the effects ofre-radiation on thermal efficiency of the receiver.

In some embodiments of the solar receivers, the high pressure solarabsorber comprises, at least in part, a single crystal super alloy. Insome embodiments, the single crystal super alloy is nickel-based. Insome embodiments, the high pressure solar absorber comprises a surfacecoating. In some embodiments, the surface coating is applied usingchemical vapor deposition. In some embodiments, the surface coating is ablack surface coating.

In some embodiments of the solar receivers, the heat exchanger comprisesa tubular coil or a shell-and-tube arrangement. In certain embodiments,the heat exchanger comprises one or more tubes having a diameter in arange of 0.5 inch to 5 inches. In certain embodiments, the heatexchanger comprises one or more tubes having a diameter of 2 inches. Incertain embodiments, the heat exchanger comprises one or more tubeshaving a wall-thickness in a range of 0.1 inch to 0.5 inch. In certainembodiments, the heat exchanger is a plate-type heat exchanger. Incertain embodiments, the heat exchanger is, at least in part, producedby a precision investment casting method. In certain embodiments, theheat exchanger comprises one or more metal-to-metal bonds formed by avacuum brazing process. In certain embodiments, the vacuum brazingprocess is activated diffusion bonding (ADB) or transient liquid phase(TLP).

In some embodiments, the solar receivers further comprise a secondaryconcentrator connected to the insulated casing at the opening. In someembodiments, the secondary concentrator comprises a plurality ofinterconnected reflective panels arranged such that incident solarradiation impinging the reflective panels is reflected toward thetransparent object. In some embodiments, the plurality of interconnectedreflective panels are arranged to form a parabolic shape. In certainembodiments, each reflective panel comprising a cooling fluid passage.

In some embodiments, power generation systems are provided comprising asolar receiver constructed and arranged to heat a first gas at apressure of less than or equal to 2 atmospheres; a rotary heat exchangerfluidically connected to the solar receiver, constructed and arranged totransfer thermal energy from the first gas to a second gas at a pressureof above 2 atmospheres; and a gas turbine fluidically connected to thesolar receiver, constructed and arranged to generate power using thesecond gas.

In some embodiments, methods of generating power are provided comprisingheating a first gas at a pressure of less than or equal to 2 atmospheresin a solar receiver; transferring thermal energy from the first gas to asecond gas at a pressure of above 2 atmospheres using a rotary heatexchanger fluidically connected to the solar receiver; and generatingpower from the second gas using a gas turbine fluidically connected tothe solar receiver.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1 includes a schematic diagram of a concentrated solar powergeneration system including a low pressure solar receiver, according toone set of embodiments;

FIGS. 2A-2C include, according to some embodiments, exemplary schematicdiagrams of heat recovery configurations that can be used with aconcentrated solar power generation system;

FIGS. 3A-3C include exemplary schematic illustrations of thermal storageunits that can be used in a thermal storage system;

FIGS. 4A-4B include, according to one set of embodiments, schematicillustrations of power tower systems;

FIG. 5 includes an exemplary schematic diagram of a concentrated solarpower generation system including a high pressure solar receiver;

FIG. 6 includes a schematic diagram of a concentrated solar powergeneration system including multiple solar receivers, according to someembodiments;

FIGS. 7A-7E include exemplary schematic illustrations of low-pressuresolar receivers;

FIGS. 8A-8C include exemplary schematic illustrations of a secondaryconcentrator;

FIGS. 9A-9C include exemplary schematic illustrations of high-pressuresolar receivers; and

FIGS. 10A-10F include exemplary schematic illustrations of concentratedsolar power generation systems.

DETAILED DESCRIPTION

Inventive concentrated solar power systems using solar receivers, andrelated devices and methods, are generally described. In someembodiments, the concentrated solar power systems include a solarreceiver used to heat a fluid at a relatively low pressure. Heat fromthe low-pressure fluid heated by the solar receiver can be transferredto a relatively high-pressure fluid, which can be used to power a gasturbine as part of, for example, a Brayton cycle. The heat exchangebetween the low- and high-pressure fluids can be accomplished via theuse of a heat exchange system.

In some embodiments, the exhaust of the gas turbine can be transportedto the solar receiver and used as the low-pressure heated fluid.Optionally, a blower can be used to provide additional ambient air tothe low-pressure solar receiver, which can be useful, for example, forregulating the flow of fluid through the system. In some embodiments, acontroller can be used to regulate the flow rate of the gas from theblower. The controller can be constructed and arranged to adjust theflow rate of the gas transported from the blower to the solar receiverbased at least in part on a condition of the gas transported from thegas turbine to the solar receiver. For example, the controller can beconstructed and arranged such that the flow rate of the gas transportedfrom the blower to the solar receiver depends on one or more of thetemperature, pressure, and/or flow rate of the gas transported from thegas turbine to the solar receiver.

The low-pressure fluid from the solar receiver, in addition to providingheat to the high-pressure working fluid within the Brayton cycle, can beused to provide heat to a thermal storage system, which can operate, forexample, by storing sensible heat from the low-pressure fluid. Thethermal storage system can be useful for operating the power cycleduring periods of low sunlight, for example, by providing heat to thelow-pressure fluid in addition to or in place of the heat provided bythe solar receiver. In some embodiments, the thermal storage system canbe operated at the high pressure of the turbine, for example, bytransporting a pressurized fluid through the thermal storage unit toheat the pressurized fluid prior to, for example, transporting thepressurized fluid to a turbine. In some embodiments, the airflow fromthe solar receiver can be switched between the thermal storage systemand the heat exchange system used to transfer heat from the low-pressurefluid to the high-pressure Brayton cycle fluid. In some embodiments, ablower can be connected to transport heated air from the thermal storagesystem into the solar receiver.

The overall efficiency of the system can be improved, in some cases, byrecovering heat from the low-pressure fluid exiting the heat exchangesystem used to transfer heat to the high-pressure fluid. For example, insome cases, the low-pressure fluid exiting the heat exchange system canbe used to generate steam to power a steam turbine in a Rankine cycle.In some instances, the low-pressure fluid exiting the heat exchangesystem can be used to provide heat to an absorption chiller, which canbe used, for example, to produce chilled water for an air conditioner.The low-pressure fluid from the heat exchange system can also be used toprovide heat for general space heating purposes (e.g., via an air toliquid heat exchanger).

Some embodiments of the invention can be used in coordination with solarpower tower systems (also known as central tower solar power plants orheliostat solar power plants). Such systems include a plurality ofheliostats arranged to redirect sunlight toward the top of a collectortower, sometimes called a central tower, on which one or more solarreceivers are mounted. In some such embodiments, the gas turbine and/orthe compressor can be mounted, along with the solar receiver, at the topof the solar tower. Other components, such as a thermal storage systemcan also be mounted at the top of, or within other parts of, the tower.

In some embodiments, low pressure solar receivers are provided that maybe used in conjunction with the power generation systems disclosedherein. The solar receivers function, at least in part, to convert solarradiation energy to thermal energy of a working fluid, e.g., a workingfluid of a power generation or thermal storage system. The solarreceivers typically comprise a low pressure fluid chamber that isdesigned and constructed, at least in part, to provide an insulatedcasing that acts to reduce or eliminate thermal losses from the solarreceiver, to contain a low pressure working fluid and/or to provide asupport structure for a solar absorber. The low pressure solar receiversalso typically comprise a transparent object (e.g., window) positionedadjacent to an opening in the receiver for receiving solar radiation.The transparent object functions, at least in part, to contain the lowpressure working fluid, to permit solar radiation to pass into the solarreceiver (where the radiation impinges the solar absorber) and toeliminate or reduce thermal losses associated with re-radiation from thesolar absorber.

Because the low pressure receiver operates at low pressure (e.g., below2 atmospheres) the chamber can be typically constructed using lessmaterial and fewer design constraints than is needed for chambers thatare subjected to higher pressures. Moreover, the low pressure designenables the use of relatively large (e.g., 1 meter to 5 meters indiameter) transparent objects that enable a high solar collectioncapacity. Thus, according to some aspects, the low pressure solarreceivers have lower cost of production and significantly largercollection capacity than currently available solar receivers.

In further embodiments, high pressure receivers are provided that may beused in conjunction with the power generation systems disclosed herein.The high pressure solar receivers function, at least in part, to convertsolar radiation energy to thermal energy of a working fluid, e.g., aworking fluid of a power generation system or thermal storage system. Insome embodiments, the high pressure receivers include an insulatedcasing housing a high pressure solar absorber that acquires thermalenergy by absorbing incident solar radiation. The high pressure fluid(e.g., fluid at a pressure of above 2 atmospheres to 50 atmospheres)entering the receiver passes through one or more fluid passages withinthe high pressure solar absorber and acquires thermal energy therein, inpart, through contact with the passage wall(s). The high pressure solarabsorber often has a black surface coating to promote absorption ofincident solar radiation and is typically constructed from a singlecrystal super alloy, e.g., a nickel-based single crystal super alloy.

Current high-pressure receivers typically use metals that are oftenlimited with respect to maximum temperatures at which they can function.For example, certain high-pressure receivers employ stainless steel orother alloys for the pressurized receiver components and these materialstypically limit the receiver exit temperatures to levels that areinsufficient to enable (at least at high efficiencies) certaindownstream uses, such as use within a Brayton power cycle. Thehigh-pressure solar receivers provided herein employ significantlyhigher temperature materials, e.g., high temperature single crystalsuper alloys, for the heat-exchanger elements and therefore can beoperated at significantly higher temperatures. In some embodiments,high-pressure absorbers are produced from nickel-based high-temperaturesuper alloy (e.g., using precision investment casting), and enablerelatively high maximum exit temperatures (e.g., temperatures of up to˜1150° C.) from the receiver. Thus, in some embodiments, the receiversmay be used within a Brayton cycle system to achieve high power output &high overall electrical efficiency.

In certain embodiments, additional heat transfer features are providedinto the internals of the heat-exchanger elements (e.g., improved crosssectional shape) to facilitate heat transfer efficiency. In someembodiments, the cast single crystal tubes are attached to headers &manifolds of similar materials via a unique vacuum brazing process knownas (ADB) activated diffusion bonding or (TLP) transient liquid phase.This joining technique enables, in some embodiments, a joint to retainfull strength & temperature capability. In some embodiments, thehigh-pressure receivers also incorporate a transparent object (e.g., aQuartz glass front window). In some embodiments, the transparent objecthas an anti-radiation reflection coating on the inside to limit theeffects of re-radiation on thermal efficiency. Moreover, in someembodiments, high resistance insulation is applied to the receivers toimprove thermal efficiency.

In some embodiments, secondary concentrators are provided. The secondaryconcentrator provides, at least in part, a mechanism for collectingconcentrated solar radiation from a primary concentrator, e.g., aheliostat field, or other source, and directing that solar radiationinto the opening of a solar receiver. The secondary concentratortypically improves the solar collection efficiency of the solarreceiver. In some embodiments, the second concentrator is constructedwith a plurality of reflective panels, each reflective panel typicallyhaving a reflective surface and a predetermined shape. The plurality ofreflective panels are typically arranged in a configuration thatfacilitates reflection of incident solar radiation toward the receiveropening. In certain embodiments the secondary concentrator includescooling pipes that function in part to deliver cooling fluid to and froma cooling passage within each reflective panel.

Certain embodiments of the inventive systems and methods describedherein can provide certain advantage(s) over traditional concentratedsolar power techniques in certain applications. For example,low-pressure components (e.g., solar receivers, storage containers,etc.) can be relatively inexpensive to manufacture and relatively safeto operate. In addition, low-operating pressures allow for the use ofrelatively large windows within the solar receiver, compared topressurized systems in which large windows can rupture at highpressures. The Brayton cycle systems described herein have a higherthermal efficiency relative to systems that employ, for example, Rankinecycles. The ability to switch the flow of low-pressure fluid betweenheat exchange for power generation and low-pressure storage can allowfor operation at night and other low-sunlight conditions. The heatintegration methods described herein can also improve overall systemperformance.

FIG. 1 shows a schematic illustration of a system 100 in whichconcentrated solar energy is used to generate power. The fluid streamsin the set of embodiments illustrated in FIG. 1 can be generally dividedinto streams comprising relatively high-pressure fluid (illustrated asdotted lines in FIG. 1) and streams comprising relatively low-pressurefluid (illustrated as solid lines in FIG. 1). It should be noted thatthese conventions are used for illustration purposes only, and are notmeant to indicate that the pressures in all relatively low-pressurestreams are the same and/or that the pressures in all relativelyhigh-pressure streams are the same.

System 100 includes a solar receiver 102 constructed and arranged suchthat at least a portion of the receiver, such as face 104 in FIG. 1, isexposed to incident solar radiation 106. The energy from the incidentsolar radiation can be used to heat a fluid within the solar receiver.In some embodiments, the solar receiver can be constructed and arrangedto operate at relatively low pressures. For example, the pressure of thefluid within the solar receiver can be up to and including about 2atmospheres, less than about 1.5 atmospheres, less than about 1.25atmospheres, less than about 1.1 atmospheres, between about 0.9 andabout 2 atmospheres, between about 0.9 and about 1.5 atmospheres,between about 0.9 and about 1.25 atmospheres, or between about 0.9 andabout 1.1 atmospheres. In some cases, the solar receiver can beconstructed and arranged such that the fluid within the receiver is notsubstantially compressed, with the exception of incidental compressionthat might occur due to the heating and/or transport of the fluid,before being transported to the receiver. For example, the fluidtransported to the solar receiver can be substantially equal to thepressure of the surrounding environment, in some cases. The reducedpressures at the receiver may allow a “window” of the receiver (e.g., atransparent portion of the receiver through which sunlight passes toheat the fluid in the receiver) to be made significantly larger than inother relatively high pressure receivers. For example, prior receiversmay be limited to a window size of about 60 cm diameter, whereas areceiver in some embodiments of the invention may have a size up toabout 150 cm or more. In some embodiments, the receivers have a windowsize of 4 meters or more.

Fluid can be transported to the solar receiver via an inlet, such asinlet line 108 in FIG. 1. Generally, fluid is transported through thesolar receiver when the sun is available to provide energy to heat thefluid. In some cases, the relatively-low pressure fluid transported tothe solar receiver can comprise the outlet stream of a turbine used togenerate power within the system. However, the relatively low-pressurefluid can also originate from other sources, in addition to or in placeof the exhaust stream of a turbine. For example, in some cases,relatively low-pressure fluid transported to the solar receiver canoriginate from the ambient environment (e.g., atmospheric air).Additional details related to the design and operation of the solarreceiver are described in more detail below.

Once the relatively low-pressure fluid has been heated within the solarreceiver, it can be transported out of the receiver, for example, viastream 110 in FIG. 1. At least a portion of the fluid within stream 110can be transported to heat exchange (or recuperator) system 112 viastream 114. Heat exchange system 112 can be used to transfer heat fromthe relatively low-pressure fluid stream (e.g., from a solar receiverand/or from a thermal storage system) to a relatively high-pressurefluid stream 116, which can be used to drive a gas turbine, as describedin more detail below.

After the heat from the relatively low-pressure stream has beentransported to the relatively-high pressure stream, the relativelylow-pressure fluid can be transported out of heat exchange system 112via stream 118. In some embodiments, stream 118 can contain residualheat, which can be recovered within heat recovery system 120 to increasesystem efficiency. Systems and methods for recovering the residual heatfrom the exhaust stream of the primary heat exchange system aredescribed in more detail below.

In the set of embodiments illustrated in system 100, power is primarilygenerated using a Brayton cycle. The Brayton cycle illustrated in FIG. 1includes gas turbine 122. While a single turbine is illustrated in FIG.1, it should be understood that the invention is not so limited, andthat, in some embodiments, multiple turbines can be employed. Forexample, in some embodiments, the power generation system includes atleast 2, at least 3, at least 4, at least 5, or more turbines. A singlegas turbine and/or the combination of multiple gas turbines can becapable of producing any suitable amount of power (e.g., at least about100 kW, at least about 500 kW, at least about 1 MW, at least about 4MW). One of ordinary skill in the art would be capable of selecting anappropriate gas turbine and/or combination of gas turbines to use, givena desired power output requirement.

In order to increase system efficiency, the gas supplied to gas turbine122 should be relatively hot and relatively highly-pressurized. Toaccomplish this, compressor 124 can be used to compress a relativelylow-pressure gas (e.g., ambient air) in stream 126 to produce relativelyhigh-pressure stream 116. As mentioned above, relatively high-pressurestream 116 can be heated by transferring the heat from heated,low-pressure stream 114 (e.g., from solar receiver 102 and/or fromthermal storage system 134) to stream 116 via heat exchange system 112to produce relatively high-pressure, relatively high-temperature stream128. In some embodiments, the compressor can be used to produce a fluidstream (e.g., a gas stream) with a pressure above 2, at least about 3,at least about 4, at least about 5, at least about 10, or at least about15 atmospheres.

As illustrated in FIG. 1, primary heat exchange system 112 includes twoheat exchangers (or recuperators), 112A and 112B. It should beunderstood that, while the figures illustrate the use of two heatexchangers, the invention is not limited to the use of heat exchangesystems including two heat exchangers, and, in some embodiments, asingle heat exchanger or more than two heat exchangers (e.g., 3, 4, 5,or more heat exchangers) can be used in the heat exchange system. InFIG. 1, the first heat exchanger 112A can be used to exchange heat atrelatively high temperatures, for example, removing heat fromhigh-temperature stream 114 to produce intermediate-temperature stream115 while transferring heat to intermediate-temperature stream 117 toproduce high-temperature stream 128. The second heat exchanger 112B canbe used to exchange heat at relatively low temperatures, for example,removing heat from intermediate-temperature stream 115 to producelow-temperature stream 118, while transferring heat to low-temperaturestream 116 to produce intermediate-temperature stream 117. Hightemperature heat exchange (e.g., at temperatures between about 800° C.and about 1250° C.) can involve the use of very expensive materials,such as specially engineered ceramics and/or high temperature superalloys. The use of multiple heat exchangers (e.g., one relatively smallinexpensive heat exchanger and one relatively small expensive heatexchanger) instead of a single large, relatively expensive heatexchanger can allow one to achieve efficient heat exchange whilereducing cost. While heat exchange system 112 in FIG. 1 is illustratedas including two heat exchangers, it should be understood that, in someembodiments, a single heat exchanger can be employed. In addition, insome cases, more than two heat exchangers can be employed in heatexchange system 112.

At least one of the heat exchangers in the heat exchanger system can beconfigured, in some embodiments, such that the heat exchangersimultaneously contains the first, low pressure fluid (e.g., gas) andthe second, high pressure fluid (e.g., gas), which may, in certainembodiments involve simultaneous flow of the first and second fluidsthrough the heat exchanger. For example, in some embodiments, at leastone heat exchanger in the heat exchanger system comprises a first inletthrough which gas at a relatively low pressure (e.g., a pressure of lessthan or equal to 2 atmospheres) is transported into the heat exchangerand a second inlet through which gas at a relatively high pressure(e.g., above 2 atmospheres) is transported into the heat exchanger whilethe first gas is transported into the heat exchanger. By configuring oneor more heat exchangers in this manner, the amount of heat transferredfrom the high temperature fluid to the low temperature fluid can beenhanced, relative to situations in which the first and second fluidsare transported subsequently through the heat exchanger (e.g., due toheat dissipation from the heat exchanger during the period between fluidflow). Heat exchangers configured in this manner can be configured tooperate in countercurrent or cocurrent mode (with flow in the same oropposite directions).

In some embodiments, one or more of the heat exchangers used to transferheat from the relatively low-pressure fluid to the relativelyhigh-pressure fluid (e.g., heat exchangers 112A and/or 112B in FIG. 1)can be a rotary heat exchanger (e.g., a ceramic rotary heat exchanger).Suitable rotary heat exchangers (e.g., rotary regenerators) for use inthe systems described herein include those described, for example, inU.S. Pat. No. RE37134, issued on Apr. 17, 2001, filed Mar. 25, 1995,entitled “Heat Exchanger Containing a Component Capable of DiscontinuousMovement”; U.S. Publication No. 2007/0089283, published on Apr. 26,2007, filed Oct. 17, 2006, entitled “Intermittent Sealing Device andMethod”; U.S. Publication No. 2008/0251234, published on Oct. 16, 2008,filed Apr. 16, 2007, entitled “Regenerator Wheel Apparatus”; U.S.Publication No. 2009/0000761, published on Jan. 1, 2009, filed Jun. 29,2007. entitled “Regenerative Heat Exchanger with Energy-Storing DriveSystem”; U.S. Publication No. 2009/0000762, published on Jan. 1, 2009,filed Jun. 29, 2007, entitled “Brush-Seal and Matrix for RegenerativeHeat Exchanger and Method of Adjusting Same”; and U.S. Publication No.2006/0054301, published on Mar. 16, 2006, filed Dec. 16, 2004, entitled“Variable Area Mass or Area and Mass Species Transfer Device andMethod.” Ceramic rotary heat exchangers can be capable of operating atrelatively high temperatures (e.g., up to about 2100° F. (1200° C.),which can allow one to supply higher temperature gas to the gas turbine,thereby increasing system efficiency. Of course, the invention is notlimited to the use of rotary heat exchangers, and, in some embodiments,one or more of the heat exchangers (e.g., the heat exchangers used totransfer heat from the relatively low-pressure fluid to the relativelyhigh-pressure fluid such as heat exchangers 112A and/or 112B in FIG. 1)can be any of a wide variety of suitable heat exchanger configurations,including, but not limited to, a plate heat exchanger, a tube heatexchanger (e.g., a shell and tube heat exchanger), etc.

In some embodiments, at least one of the heat exchangers can be ametallic heat exchanger. The first and second heat exchangers can be ofdifferent types. For example, in some embodiments, one of the heatexchangers within the heat exchange system can be a ceramic heatexchanger (e.g., a ceramic rotary heat exchanger, a ceramic plate heatexchanger, a ceramic tube heat exchanger, etc.) while a second of theheat exchangers can be a metallic heat exchanger. For example, gas fromthe solar receiver can be transported to a ceramic heat exchanger (wherea relatively high maximum temperature might be observed), andsubsequently transported to a metallic heat exchanger (where the maximumtemperature might be lower than that observed in the ceramic heatexchanger).

In some embodiments, the system can include a heat exchanger that isconfigured to be operated at a relatively high temperature. For example,in some embodiments, the system can include one or more heat exchangers(e.g., heat exchangers 112A and/or 112B in FIG. 1) that can be operatedabove temperatures of 1500° F. and in some embodiments at temperaturesof up to 1800° F. In some embodiments, the system can include one ormore heat exchangers that can be operated at temperatures of up to 2100°F. or even to 2500° F. High temperature heat exchangers can comprise oneor more materials configured to withstand high temperature operationincluding, for example, one or more ceramics (e.g., aluminum oxides,iron oxides, silicon oxides, magnesium oxides, etc.). In someembodiments, the heat exchanger can comprise one or more metals (e.g., asuper alloy such as those comprising nickel, chromium, titanium,tungsten, molybdenum, tantalum, columbium, and the like, including anyof the super alloys described elsewhere herein. As specific examples,all or part of a high temperature heat exchanger can be formed of Alloy230®, Alloy 214®, and/or Alloy 556® from Haynes International.

In some embodiments, the fluid within high-pressure, high-temperaturestream 128 can be transported directly to gas turbine 122, where it canbe used to produce power. The gas turbine can be constructed andarranged to operate using incoming gas streams with relatively highpressures. In some embodiments, the gas stream fed to the gas turbinehas a pressure of above 2, at least about 3, at least about 4, at leastabout 5, at least about 10, or at least about 15 atmospheres. In someinstances, for example during startup or during periods when thetemperature of the fluid in stream 114 is relatively low (e.g., duringperiods of low sunlight and/or when storage container 112 (describedbelow) is not sufficiently heated to supply high-temperature fluid), anoptional supplemental heater 130 can be employed to supply additionalheat to the fluid in stream 128, producing stream 128B which can betransported to gas turbine 122. Supplemental heater 130 can comprise,for example, an auxiliary combustor, sometimes called a boost combustor,that burns fuel to supply additional heat. One of ordinary skill in theart would be capable of selecting an appropriate device to provide therequired amount of supplemental heat, given the power demands andoperating conditions of a given system. For example, heater 130 mightcomprise an induced flow combustor.

Once the gas in stream 128 (or 128B) has been expanded, a relativelylow-pressure, low-temperature turbine exhaust stream 132 can beproduced. As mentioned above, in some embodiments, the turbine exhauststream 132 can be fed to the solar receiver 102, where it can bereheated and used to supply heat to heat exchange system 112. Routingthe turbine exhaust in this way can be beneficial, as the turbineexhaust may contain residual heat that would otherwise be lost if theexhaust were vented directly to the atmosphere.

In some embodiments, system 100 can include optional thermal storagesystem 134. In some embodiments, the thermal storage system can includea single thermal storage unit, while in other embodiments, the thermalstorage system can include a plurality of thermal storage units. Thethermal storage system can be used to store heat (e.g., sensible heat)for use during periods of relatively low sunlight and/or during startupof the system. During periods of relatively high sunlight, at least aportion of the fluid exiting the solar receiver (e.g., via stream 110)can be transported to the thermal storage system 134 (e.g., via stream136), where the heat can be retained for later use. During periods oflow sunlight, a relatively low-temperature fluid can be transported intothe thermal storage system via stream 138. The heat stored withinthermal storage system 134 can be used to heat the relativelylow-temperature fluid to produce high-temperature fluid, which can betransported to heat exchange system 112, e.g., via streams 136 and 114.In some embodiments, the fluid supplied to stream 138 can comprise theexhaust stream 132 of turbine 122. For example, in some cases duringperiods of low sunlight, little or no fluid might be supplied to solarreceiver 102 via stream 108, and low-pressure fluid from the exhauststream 132 of turbine 122 (and, optionally, some fluid from the ambientatmosphere) can be re-directed to thermal storage system 134 via conduit138. In some embodiments, a controller and valves can be used toregulate the distribution of low-pressure fluid through solar receiver102 and thermal storage system 134.

In some embodiments, optional blower 140 can be incorporated into thesystem. Any suitable type of blower can be included in the system; theblower can comprise, for example, an electric driven induction flow fan.The blower can be used, for example, to transport the gas turbine exitstream (e.g., stream 132 in FIG. 1) through the solar receiver duringperiods of relatively high sunlight. In addition, blower 140 can be usedto provide the power to circulate hot air through the thermal storagesystem during periods of high sunlight. In some embodiments, blower 140can be used to transport heated air from thermal storage system 134 tothe solar receiver 102 (e.g., via pathway 138) to provide pre-heated airto the solar receiver (e.g., during periods of relatively low sunlight).In some embodiments, blower 140 can be shut down during periods ofrelatively low sunlight when the thermal storage system can provide heatfor the system.

The blower can be arranged, in some cases, to accept ambient air orfluid from another source in addition to the exhaust gas from the gasturbine. In this way, the blower can be used to control the overall flowrate of the fluid within the relatively low-pressure section (i.e., fromthe exhaust of the gas turbine, through heat exchange system 112, andthrough optional heat recovery system 120). For example, when higherflow rates through the low-pressure section are desirable, the blowercan take in a relatively large amount of fluid from the ambient oranother, non-turbine exhaust source. When lower flow rates through thelow-pressure section are desirable, the blower can take in a relativelysmall amount of (or no) fluid from the ambient or another, non-turbineexhaust source.

As noted above, residual heat within stream 118 from heat exchangesystem 112 can be exchanged within optional heat recovery system 120.Heat recovery system 120 can include a variety of configurations. Forexample, in some cases, a Rankine bottoming cycle can be employed torecover residual heat. FIG. 2A includes a schematic diagram illustratingthe recovery of energy from stream 118 using a Rankine cycle. In FIG.2A, stream 118, originating from heat exchange system 112, is fed to aheat exchange boiler 210. The heat within stream 118 can transferred toanother fluid stream containing water (e.g., stream 211 in FIG. 2A),which can result in the production of steam or hot water. The steamproduced during this exchange of heat can exit via stream 212. Boiler210 can also produce effluent stream 213, which can include cooled fluidfrom stream 118. Stream 212 can be fed to steam turbine 214, where itcan be used to produce energy and exhaust stream 216. Exhaust stream 216can be condensed to water in optional condenser 218, to produce heat(which can be used in other areas of the process) a condensed stream. Asshown in FIG. 2A, the condensed stream from the condenser is illustratedas being used as heat exchange boiler inlet stream 211, which can bere-heated to generate steam. Optionally, steam turbine exhaust stream216 can be used as heat exchange boiler inlet stream 211.

In some instances, an absorption chiller can be used to recover residualheat from stream 118. FIG. 2B includes a schematic illustration of onesuch set of embodiments. In FIG. 2B, stream 118 is transported toabsorption chiller 220, where the heat from stream 118 is used toprovide energy to the absorption chiller necessary to cool a relativelywarm fluid in stream 222 (e.g., ambient air) to produce a cooled fluidstream 224. In addition to producing cooled fluid stream 224, theabsorption chiller can produce exhaust stream 226, which contains fluidfrom stream 118 that has been cooled. Cooled stream 224 can be used, forexample, as part of an air conditioning system. As another example,cooled stream 224 might be used to cool system components (e.g., the gasturbine), for example, during operation in very hot climates (e.g.,temperatures of 100° F. or above). One of ordinary skill in the artwould be capable of selecting a suitable absorption chiller based uponthe required cooling load, temperature and flow rate of incoming fluidstream 118, and other design parameters.

In still other cases, the residual heat within stream 118 can be used toprovide heat (e.g., within other areas of the process and/or to areasoutside the power generation process). FIG. 2C includes an exemplaryschematic illustration of one such set of embodiments. In FIG. 2C,stream 118 is transported to heat exchanger 230, where it is used toheat relatively cool fluid in stream 232 (e.g., ambient air) to producea heated fluid stream 234. In addition, exhaust stream 236, whichcontains fluid from stream 118 that has been cooled, can be produced.Heated stream 234 can be used, for example, to produce hot water orother liquids for use in a running water system, a space heating system(e.g., to provide heat one or more rooms within a building or othersuitable structure), or any other suitable system in which heated fluidsare required. One or ordinary skill in the art would be capable ofselecting a suitable heat exchanger based upon the required heatingload, temperature and flow rate of incoming fluid stream 118, and otherdesign parameters.

The inclusion of heat recovery system 120 can lead to relatively largeincreases in overall system efficiency. Generally, overall systemefficiency is calculated as the power produced by the system (in theform of electricity and/or in the form of a heated or cooled stream thatcan be used in another system, such as streams 224 and 234 in FIGS. 2Band 2C) divided by the power of the solar energy incident on the solarreceiver and multiplied by 100%. In embodiments employing the Rankinebottoming cycle illustrated in FIG. 2A, the overall efficiency canapproach about 50% (e.g., between about 40% and about 50%). For systemsthat include an absorption chiller such as the system illustrated inFIG. 2B, overall system efficiency can approach about 60% (e.g., betweenabout 40% and about 60%). The overall efficiency of power generationsystems that employ a heat exchanger to provide heat to other parts ofthe power generation system and/or external systems can approach about80% (e.g., between about 40% and about 80%).

As noted above, the thermal storage system 134 in system 100 can includeone or more thermal storage units. The thermal storage unit(s) canenable a practical and cost effective method to achieve thermal storageof CSP energy for use in generating electricity during hours with no orlow sunlight. In some embodiments, a thermal storage unit can comprise atank in which solid media with passages through which the fluid flows islocated to store the thermal energy at relatively high temperatures(e.g., at least about 1800° F., at least about 2000° F., or higher).

Exemplary illustrations of suitable thermal storage units are shown inFIGS. 3A-3C. FIG. 3A includes a cross-sectional view of a storage unit310, including lines 312 and 314, each of which can function as an inletor an outlet. Unit 310 also includes plate 316A that includes aplurality of passageways. Plate 316A is designed in this manner so fluidcan be transported through the plate while the plate supports thermalstorage media within volume 318, preventing the thermal storage mediafrom entering line 314. In addition, unit 310 can include plate 316B,which can also comprise a plurality of passageways. By designing plate316B in this manner, fluid can be transported from volume 318 andthrough plate 316B without entraining thermal storage media as the fluidexits line 312. By avoiding the transport of thermal storage media outof the thermal storage unit 310, one can reduce damage (e.g., erosiondamage) to the turbine, blower, solar receiver, or other systemcomponents that may occur when the media contact these components.

Thermal storage unit 310 can be fabricated using a variety of materialsincluding, for example, metals (e.g., stainless steel). In someembodiments, thermal storage unit 310 is configured such that it is acertified pressure vessel (e.g., ASME-certified, EN13445 certified, or apressure vessel meeting a similar set of certification standards). Inaddition, plates 316A and 316B can be fabricated from any suitablematerial, including metals (e.g., stainless steel, refractory metalssuch as tungsten, and the like), ceramics, and/or combinations of thesematerials.

Thermal storage unit 310 can be fabricated in sections, such that two ormore of the sections may be bolted together to assemble a storage unithaving a desired volumetric capacity. Fabrication of the storage unit insections facilitates factory construction, transport and onsite assemblyof storage units having relatively large volumetric capacity. In someconfigurations sections of the storage unit may be in the range of 8feet to 16 feet in length and 8 feet to 16 feet in diameter. In someconfigurations sections of the storage unit may be approximately 12 feetin length and 10 feet to 12 feet in diameter.

The passageways within plate 316A and/or 316B can be configured toimpart a desired flow profile within volume 318. For example, the sizes(e.g., diameters, lengths), cross-sectional shapes, and/or flow anglesof the pathways within plates 316A and/or 316B can be selected toachieve a desired flow profile. The openings of the fluid passagewaysone or both sides of plates 316A and/or 316B can be arranged in anysuitable pattern including, for example, a honeycomb pattern.

As noted above, lines 312 and 314 can each function as an inlet or anoutlet. For example, in some instances in which the thermal storagemedia within unit 310 is being heated by an incoming fluid (e.g., at atemperature of between 1800° F. and 1900° F.), line 312 can function asan inlet and line 314 can function as an outlet. In such cases, plate316A can prevent thermal storage media from being entrained in theheating fluid and being transported through outlet 314. In someinstances in which the thermal storage media within unit 310 is beingused to heat an incoming fluid (e.g., at an incoming temperature ofbetween 100° F. and 1200° F.), line 314 can function as an inlet andline 312 can function as an outlet. In such cases, plate 316B canprevent thermal storage media from being entrained in the heated fluidand being transported through outlet 312. The direction of fluid flowwithin unit 310 can be freely changed, depending on the mode ofoperation of the power generation system.

In some cases, a first portion of the gas heated by the solar receivercan be transported to the thermal storage system and a second portion ofthe gas heated by the solar receiver can be transported to the heatexchange system (i.e., the airflow from the solar receiver can beswitched between the thermal storage system and the heat exchange systemused to transfer heat from the low-pressure fluid to the high-pressureBrayton cycle fluid). In some cases, substantially all of the gas fromthe solar receiver is transported to the thermal storage system over afirst period of time, and substantially all of the gas from the solarreceiver is transported to the heat exchange system over a second periodof time that does not overlap with the first period of time. Forexample, substantially all of the exhaust stream from the solar receivermight be transported to the thermal storage system over a first periodof time, and at a later time, the flow from the solar receiver can beswitched such that substantially all of the solar receiver exhaust istransported to the heat exchange system. In other cases, a first portionof the gas from the solar receiver is transported to the thermal storagesystem over a first period of time, and a second portion of the gas fromthe solar receiver is transported to the heat exchange system over thefirst period of time. Stated another way, the exhaust stream from thesolar receiver can be split such that, simultaneously, a first portionof the solar receiver exhaust is transported to the thermal storagesystem and a second portion of the solar receiver exhaust is transportedto the heat exchange system.

In some embodiments, the thermal storage system (including any thermalstorage unit(s) within the thermal storage system) can be constructedand arranged to operate at relatively low pressures during at least aportion of the period of time over which system 100 is operated. Forexample, the pressure of the fluid within the thermal storage system(including any thermal storage unit(s) within the thermal storagesystem), for example, during heating of the thermal storage systemand/or during heating of a fluid being transported through the thermalstorage system, can be up to and including 2 atmospheres, less thanabout 1.5 atmospheres, less than about 1.25 atmospheres, less than about1.1 atmospheres, between about 0.9 and about 2 atmospheres, betweenabout 0.9 and about 1.5 atmospheres, between about 0.9 and about 1.25atmospheres, or between about 0.9 and about 1.1 atmospheres. In somecases, the thermal storage system can be constructed and arranged suchthat the fluid within the thermal storage system is not substantiallycompressed, with the exception of incidental compression that mightoccur due to the heating and/or transport of the fluid, before beingtransported to the thermal storage system. For example, the fluid withinthe thermal storage system can be substantially equal to the pressure ofthe surrounding environment, in some cases. In some embodiments, thethermal storage system 134 is operated at relatively low pressures whenbeing heated by a low-pressure fluid (e.g., low pressure fluid in stream136 from solar receiver 102). In some embodiments, thermal storagesystem 134 is operated at relatively low pressures when being used topre-heat a fluid that is to be transported to turbine 122.

It should be understood that the invention is not limited to the use oflow-pressure fluid within thermal storage system 134, and that, in someembodiments, high-pressure fluid can be transported through thermalstorage system 134 during operation of system 100. For example, in someembodiments, a relatively high-pressure fluid (e.g., at a pressure ofabove 2 atmospheres, at least about 2.1 atmospheres, at least about 2.25atmospheres, at least about 2.5 atmospheres, at least about 3atmospheres, at least about 4 atmospheres, at least about 5 atmospheres,at least about 10 atmospheres, or at least about 15 atmospheres, and, insome embodiments, up to 50 atmospheres) can be transported through andheated by thermal storage system 134 (e.g., after thermal storage system134 has been heated by a fluid, such as a low-pressure fluid from solarreceiver 102). After the high-pressure fluid is heated by thermalstorage system 134, it can be transported to turbine 122 to generatepower, in some embodiments.

In many previous thermal storage systems, high pressures are employed,which can increase the expense required to construct the systems. Otherprevious thermal storage systems have used a variety of salts or othermaterials that undergo a phase change, many of which materials were alsovery expensive. By being unpressurized and fully factory produced alongwith low-cost fill (thermal storage) media this approach dramaticallyreduces CSP thermal storage system cost. Using the CSP thermal storagetanks in modular form as part of the CSP tower could further improve thecapital costs associated with the system.

The thermal storage units within the thermal storage system can bemodular, in some cases, which can allow one to easily scale a system inorder to allow a CSP system to operate to produce a given power for agiven time without low or no sunlight. For example, FIG. 3B includes asystem in which a single unit is used to store thermal energy. In FIG.3C, two thermal storage units are connected (e.g., by rotating caps 320such that lines 312 face each other) to double the thermal storagecapacity. Of course, the amount of energy delivered by the thermalstorage unit(s) can be altered in other ways by, for example, onlypartially filling one or more units with media and/or limiting thedegree to which one or more sections of a single unit are heated (whichmight include establishing a thermal gradient along the longitudinalaxis of one or more storage units).

In some embodiments, the tanks can be sized to achieve relatively easytransport. For example, each thermal storage unit could be between about2 and about 12 feet in diameter, and up to 40 feet long to enable easyshipment. The thermal storage units can be filled on site or prior todelivery to the site, which can allow for cost effective production andreduce on site construction cost and/or schedule delays.

A variety of fill media can be used in the thermal storage unit(s) inthe thermal storage system. The fill media can comprise a variety ofmaterials with high heat capacities that are able to retain theirstructures at high temperatures, such as ceramics and other refractorymaterials. Exemplary materials include, but are not limited to,materials comprising aluminum oxides, iron oxides, silicon oxides,and/or magnesium oxides such as fire brick, mullite, magnetite, PYROGRAN 35/38, PYRO KOR 60NR, PYRO KOR 95NK, and/or PYROFER 70. In someembodiments, the thermal storage media has a heat capacity of at leastabout 600 J/kg K, at least about 800 J/kg K, or at least about 900 J/kgK. It can be advantageous, in some embodiments, to use materials withrelatively low densities (e.g., less than about 5 g/cm³, less than about3 g/cm³, or less than about 2 g/cm³).

The thermal storage media within the thermal storage unit(s) can be ofany suitable form factor and size. For example, pellets (e.g.,substantially spherical pellets or pellets with any of the shapesdescribed below) with maximum cross-sectional diameters in mm, cm, orlarger length scales can be used as the thermal storage media, in someinstance. In some embodiments, the thermal storage media can comprisepellets, and at least about 50%, at least about 75%, at least about 90%,at least about 95%, or at least about 99% of the pellets have maximumcross-sectional diameters of less than about 100 cm, less than about 10cm, less than about 1 cm, between about 1 mm and about 100 cm, orbetween about 1 cm and about 100 cm. Suitable pellet shapes include, butare not limited to, shapes that are substantially rectangular prisms(e.g., bricks, substantially cubic shapes), substantially triangularprisms, substantially spheres, bow ties, honeycombs, saddles, and thelike. In one set of embodiments, the thermal storage media can compriseelongated tubes through which heated fluid is transported.

In some embodiments, the interior of the thermal storage unit(s) can belined with a thermally insulating material and/or the outside of thethermal storage unit(s) can be covered with a thermally insulatingmaterial to reduce heat loss to the atmosphere. For example, when thetank is manufactured out of metal, the tank can be lined with and/orcovered with a refractory material (e.g., ceramics such as alumina,silica, magnesia, and the like). In some embodiments, the refractorymaterial can be cast in place and/or can comprise a multi-layeredstructure in which the density and/or heat capacity can vary from layerto layer. In some embodiments, the thickness of the thermally insulatinglining within the unit(s) can be between about 5 inches and about 15inches (e.g., for a tank with a diameter up to 12 feet and a length ofup to 40 feet). In some embodiments, the thickness of the thermallyinsulating material on the exterior of the thermal storage unit(s) canbe up to 1 foot or up to 2 feet in thickness.

As noted above, the components of the CSP system can be positioned invarious parts of a solar power tower. FIG. 4A includes a schematicillustration of one set of power tower embodiments. The system 400 inFIG. 4A includes solar receiver 410 fluidically connected to turbinepackage 412, which can include a gas turbine and a compressor. In thisembodiment, the turbine package 412 is made as a single modular unitthat can be completely assembled at a factory, shipped to an operationsite (e.g., by truck or railroad car), and placed (e.g., by crane) ontoa tower structure 414. The turbine package 412 may include not only acompressor and gas turbine, but also a heat exchanger, or recuperator,unit, an electric generator and related power electronics, asupplemental heater and/or control valves and other components tocontrol the operation of one or more portions of the power generationsystem. The turbine package 412 may be made and shipped as a single unitwith the receiver 410 (which in this embodiment also includes thesecondary collector), or the package 412 and receiver 410 may be made asseparate modular units and assembled together on the tower structure 414at the operation site. By making turbine and receiver sections in amodular arrangement, manufacturing of the modular units may be made moreefficient. That is, the turbine package 412 and receiver 410 may be madein a factory setting, with skilled technicians building and testing thepackage 412 and receiver 410 before being sent to an operation site. Thepackage 412 and receiver 410 may be tested in real conditions, e.g., ona tower or other structure that received sunlight from a heliostatfield, or in more artificial conditions. For example, the turbinepackage 412 may be tested by supplying heated air or other fluid to thepackage 412 that is heated by fuel combustor or other suitablearrangement. Similarly, the receiver 410 may be tested by illuminatingthe receiver 410 with artificial light or other radiation that does notoriginate from a heliostat field. In this way, the package 412 andreceiver 410 may be tested individually, or as a functioning whole,under different conditions (such as low light levels, high light levels,high and/or low ambient temperature conditions, high and low poweroutput conditions, etc.) As a result, steps may be taken to help ensurethat fully functioning turbine package 412 and/or receiver 410 units areshipped to an operation site.

In some embodiments, one or more thermal storage units can beincorporated as part of a tower structure 414 which can, for example,allow for relatively easy assembly and further reduce the overall costof the CSP system. For example, thermal storage media can be storedwithin tower structure 414, which can serve as the thermal storage unit.For example, in the set of embodiments illustrated in FIG. 4A, towerstructure 414 can be filled with thermal storage medium and providethermal storage capability for system 400. In another embodiment, thetower structure 414 may be arranged to house one or more thermal storagetanks like that shown in FIGS. 3A-3C. If two or more tanks are provided,the tanks may be stacked within the tower structure 414. Arranging thetanks within the tower structure 414 may provide different features suchas reducing the overall footprint of the power generating unit,providing additional thermal cover for the tanks, and/or enhancing thestrength of the tower structure 414. For example, the tanks may beincorporated into the tower structure 414 so as to not only providethermal storage, but also provide structural support for the towerstructure 414. Like the receiver 410 and turbine package 412, the energystorage tanks and/or tower structure 414 may be made in one or moremodular units that are shipped to an operation site and assembledtogether.

FIG. 4B illustrates another set of embodiments that includes thermalstorage unit 416, independent of tower structure 414. That is, in thisembodiment, a thermal storage tank 416 is mounted to the top of thetower structure 414 with the receiver 410 and turbine package 412. Thereceiver 401, turbine package 412 and tank 416 may be made as a singlemodular unit that may be manufactured at a factory and shipped (e.g., bytruck or railcar) to an operation site and placed on top of a towerstructure 414, or the receiver 410, turbine package 412 and/or tank 416may be made as separate modular units. A modular structure maysignificantly reduce assembly costs at the operation site, e.g., becausethe receiver 410, turbine package 412 and tank 416 may be placed bycrane on the tower structure 414 and be ready for operation with onlyrelatively minimal assembly at the operation site. For example, if madeas a single unit, placement of the receiver 410, turbine package 412 andtank 416 may require only electrical power hookups and connection to thetower 414 for the system to be ready for energy generation.

One advantage provided by aspects of the invention relates to thedecreased overall weight of the power generation system, e.g., includingthe receiver 410 and turbine package 412 of FIG. 4A. In one set ofembodiments, the total weight of the receiver 410 and turbine package412 may be approximately 50 tons per MWe power output. For example, a 1MWe system may have the receiver 410 and turbine package 412 weighapproximately 100,000 pounds (or 50 tons). Of course, the weight of thecomponents may vary depending on a variety of factors, and thus theweight per MWe power output may vary from about 25 to 100 tons/MWe ormore. (It is envisioned that tower-based solar power generation systemaccording to aspects of the invention may be constructed for poweroutput ranging from about 100 kWe to 5 MWe. Of course, smaller andlarger output systems are possible, but may not be economically feasible(e.g., small output systems may not be economically justify installationcosts) or technically feasible (e.g., large output systems may havereceiver and turbine package weights that are too large for sensibletower deployment.)

Although the embodiments shown in FIGS. 4A and 4B show the receiver 410,turbine package 412 and/or tank 316 arranged in a modular format, thevarious components of the power generation system need not be arrangedin modular units. Instead, in some embodiments, the individual pieces ofthe system (such as a gas turbine, compressor, recuperators, receiver,collector, etc.) may be assembled in place on the tower. Thus, aspectsof the invention are not necessarily limited to modular arrangements ofcomponents that are attached to a tower structure 414.

As mentioned above, in some embodiments, the power generation system caninclude a solar receiver operating at a relatively high pressure (e.g.,above 2 atmospheres, at least about 3 atmospheres, at least about 4atmospheres, at least about 5, at least about 10, or at least about 15atmospheres) in place of or in addition to the solar receiver operatingat a relatively low pressure.

FIG. 5 includes an exemplary schematic diagram of a concentrated solarpower generation system 500 including a high pressure solar receiver. InFIG. 5, fluid stream 526 (e.g., comprising ambient air) is fed tocompressor 524, where it is compressed to a relatively high pressure.High pressure stream 516 from compressor 524 is then fed to heatexchange system 512, which can comprise one or more heat exchangers. Inthe set of embodiments illustrated in FIG. 5, two heat exchangers (512Aand 512B) are shown, although in other embodiments a single heatexchanger or more than two heat exchangers may be used. For example, insome cases, a single rotary heat exchanger (e.g., a ceramic rotary heatexchanger, a metal rotary heat exchanger) can be used in heat exchangesystem 512. In other cases, two or more rotary heat exchangers (e.g.,ceramic rotary heat exchangers, metallic rotary heat exchangers, orcombinations of the two) can be used in heat exchange system 512.

In the set of embodiments illustrated in FIG. 5, heated high pressurestream 528 from heat exchange system 512 is transported to high pressuresolar receiver 502, where it is further heated via incident solarradiation 506 passed through surface 504. High pressure, hightemperature stream 510 is then transported to turbine 522 (e.g., a gasturbine, which can be part of a Brayton cycle), where the stream is usedto produce power. Exhaust stream 514 from gas turbine 522 can betransported to heat exchange system 512, where the residual heat in thestream can be used to pre-heat the compressor exhaust stream 516.Exhaust stream 518 can, in some cases, be used to provide energy to aheat recovery system 520, which can comprise any of the componentsdescribed above in relation to heat recovery system 120. The highpressure receiver system outlined in FIG. 5 can be useful, for example,in embodiments in which a single crystal nickel receiver is employed.

FIG. 6 includes an exemplary schematic illustration of a powergeneration system 600 in which two solar receivers are employed. In theset of embodiments illustrated in FIG. 6, fluid stream 626 (e.g.,comprising ambient air) is fed to compressor 624, where it is compressedto a relatively high pressure. High pressure stream 616 from compressor624 is then fed to heat exchange system 612, which can comprise one ormore heat exchangers. In the set of embodiments illustrated in FIG. 6,two heat exchangers (612A and 612B) are shown, although in otherembodiments a single heat exchanger or more than two heat exchangers maybe used. For example, in some cases, a single heat exchanger (e.g., arotary heat exchanger such as a ceramic rotary heat exchanger or a metalheat exchanger, or any other type of high temperature heat exchanger)can be used in heat exchange system 612. In other cases, two or moreheat exchangers (e.g., two or more rotary heat exchangers such asceramic rotary heat exchangers or metallic heat exchangers, orcombinations of the two, or two or more of another type of hightemperature heat exchanger) can be used in heat exchange system 612.

In FIG. 6, a portion of heated high pressure stream 628 from heatexchange system 612 is transported to high pressure solar receiver 602,where it is further heated via incident solar radiation 606 passedthrough surface 604. In some cases, a portion of high pressure stream628 can be transported to combustor 630, where it can be further heated.A portion of high pressure, high temperature stream 610 exiting the highpressure solar receiver 602 can be transported to combustor 630, whereit can be further heated, if necessary.

In some cases, at least a portion of high pressure, high temperaturestream 610 exiting the high pressure solar receiver 602 can betransported to a thermal storage system 634. Stream 610 can be used todeliver energy to the thermal storage system, in some embodiments. Insome cases, thermal storage system 634 can absorb heat from a lowpressure stream exiting low pressure solar receiver 603, described inmore detail below. In some such cases, a high pressure, high temperaturestream 635 exiting thermal storage system 634 can be transported tocombustor 630, where it can be optionally further heated. The fluidstreams transported to combustor 630 can be subsequently transported togas turbine 622 via stream 637, where they can be used to generatepower.

The turbine exhaust stream 614 can be transported to heat exchangesystem 612, where the residual heat can be used to pre-heat compressorexhaust stream 616 before it is transported to high pressure solarreceiver 602. In some cases, a portion (or all) of the exhaust stream618 from heat exchange system 612 can be transported to a second, lowpressure solar receiver 603 (in some cases, via optional blower 640).The fluid within the low pressure solar receiver 603 can be heated viaincident solar radiation 607 transmitted through surface 605. The lowpressure receiver exhaust stream 650 can be transported to thermalstorage system 634, where it can be used to supply heat (which can beused, for example, to heat all or part of high pressure solar receiverexhaust stream 610). The low pressure stream 652 exiting thermal storagesystem 634 can be used, in some embodiments, within thermal recoveryregion 621, which can include any of the components described above inrelation to heat recovery system 120.

In some cases, the thermal storage system can include a first portionconstructed and arranged to be operated at a relatively high pressure(e.g., at least about 3, at least about 4, at least about 5, at leastabout 10, or at least about 15 atmospheres), and a second portionconstructed and arranged to be operated at a relatively low pressure(e.g., equal to or less than about 2, less than about 1.5, less thanabout 1.25, or less than about 1.1 atmospheres, between about 0.9 andabout 2 atmospheres, between about 0.9 and about 1.5 atmospheres,between about 0.9 and about 1.25 atmospheres, or between about 0.9 andabout 1.1 atmospheres). For example, in the set of embodimentsillustrated in FIG. 6, thermal storage system 634 includes a firstportion constructed and arranged to handle the flow of low-pressurestream 650 and a second portion constructed and arranged to handle theflow of high-pressure stream 610.

In some embodiments, a portion of exhaust stream 618 from heat exchangesystem 612 can be transported to thermal recovery region 620, which caninclude any of the components described above in relation to heatrecovery system 120.

Many of the components illustrated in the figures are fluidicallyconnected. As a specific example, receiver 102 and heat exchange system112 in FIG. 1 are illustrated as being directly fluidically connected.In addition, in FIG. 1, heat recovery system 120 and gas turbine 122 areillustrated as being fluidically connect (although not directlyfluidically connected). Two components are said to be “fluidicallyconnected” when they are constructed and arranged such that a fluid canflow between them. In some cases, two components can be “directlyfluidically connected,” which is used to refer to a situation in whichthe two components are constructed and arranged such that a fluid canflow between without being transferred through a unit operationconstructed and arranged to substantially change the temperature and/orpressure of the fluid. One of ordinary skill in the art would be able todifferentiate between unit operations that are constructed and arrangedto substantially change the temperature and/or pressure of a fluid(e.g., a compressor, a condenser, a heat exchanger, etc.) and componentsare not so constructed and arranged (e.g., a transport pipe throughwhich incidental heat transfer and/or pressure accumulation may occur).It should be understood that, while two components might be illustratedas being directly fluidically connected in the figures, otherembodiments can include arrangements in which they are fluidicallyconnected but not directly fluidically connected.

In some embodiments, solar receivers, such as those shown in FIGS. 7A-D,are designed and constructed to be used in conjunction with the powergeneration systems provided herein. The exemplary solar receivers inFIGS. 7A and 7B comprise a low pressure fluid chamber 700 that isdesigned and constructed to provide an insulated casing 700, which actsto reduce or eliminate thermal losses from the solar receiver and tocontain a low pressure working fluid. The low pressure solar receiverscomprises a transparent object 703 positioned at the front of the lowpressure fluid chamber 700 adjacent to the opening 708 for receivingsolar radiation.

In the embodiments depicted in FIGS. 7A and 7B, a fluid path is definedwithin the low pressure fluid chamber 700, such that a relatively lowtemperature working fluid (e.g., a fluid having a temperature in a rangeof 300° C. to 800° C.) entering the fluid inlet 702 at the rear of thereceiver, passes through the receiver around the periphery of a liner709 into a front region of the fluid chamber 700 and across thetransparent object 703 (e.g., a window). By passing across thetransparent object 703, the relatively low temperature working fluidacts, in part, to cool the transparent object 703, which is heating, inpart, by incident solar radiation and thermal radiation from a solarabsorber 704. The relatively low temperature working fluid passesthrough the solar absorber 704 wherein it is further heated by the solarabsorber 704. Within the solar absorber the relatively low temperatureworking fluid is converted to a relatively high temperature workingfluid (e.g., a fluid having a temperature in a range of above 800° C. to1200° C.). The relatively high temperature working fluid exits the lowpressure fluid chamber 700 through a fluid outlet 701. After leaving thesolar receiver, in some embodiments, the relatively high temperatureworking fluid is directed to a gas turbine system, a thermal storagesystem (e.g., a sensible heat storage system), or other thermal energysystem, as is exemplified elsewhere herein.

Typically, a solar absorber, such as that depicted in FIG. 7A, isconstructed of a material that can withstand relatively hightemperatures (e.g., temperatures in excess of 1000° C.) and that hassufficient thermal properties (e.g., thermal conductivity, emissivity)to absorb thermal energy from incident solar radiation and transferthermal energy to a working fluid passing within the solar receiver. Insome cases, the solar absorber is constructed of a material such as ametal, (e.g., high-temperature alloy, heat resistant cast alloy), arefractory material (e.g., a ceramic) or a carbon-based material. Thesolar absorber is often constructed of a ceramic material such as aglass ceramic, silicon carbide, silicon nitride, or silicon oxide.

The solar absorber 704 of a low pressure receiver, such as that depictedin FIG. 7A, typically has a high surface area to facilitate the transferof thermal energy to a working fluid passing within the solar receiver.The solar absorber 704, in some embodiments, is designed and constructedto have a network (e.g., a honeycomb network, a shell and tube network,a foam network, etc.) of fluid passages through which the working fluidpasses. The solar absorber 704 is immobilized within the low pressurechamber such that a relatively low temperature working fluid travelingwithin the fluid flow path of the low pressure chamber 700 is directedto enter the solar absorber 704, passing through the network of fluidpassages of the solar absorber 704, wherein the working fluid acquiresheat from the solar absorber 704.

While the solar absorber 704 depicted in FIGS. 7A and 7B has an angularshape, the solar absorbers are not so limited and other suitable shapesmay be constructed and used with the solar receivers disclosed herein.For example, a solar absorber may have a planar shape, an ellipticalshape, a parabolic shape, a disc shape, a polyhedron shape or othersuitable shape.

The transparent object 703 of the solar receiver depicted in FIG. 7A ispositioned at the front of the low pressure fluid chamber 700 adjacentto the opening 708 for receiving solar radiation. The outer rim of thetransparent object 703 is fitted within a recess 705 of the low pressurefluid chamber 700. The transparent object 703 and the low pressurechamber 700 are typically constructed of materials having differentcoefficients of thermal expansion. For example, the transparent object703 is typically constructed of a glass material (e.g., silica, quartz,etc.), whereas the low pressure chamber 700 is typically constructed ofa metal (e.g., stainless steel, aluminum). When the transparent object703 and low pressure chamber 700 are subjected to thermal fluctuations,such as those which occur between activity and lack of activity of thesolar receiver, there is often differential thermal expansion andcontraction of the two components. Thus, the connection between thetransparent object 703 and the low pressure fluid chamber 700 musttypically be designed and constructed to accommodate differentialmovement between the two components.

In some embodiments, a flexible seal is provided between an interface onthe low pressure fluid chamber 700 and the transparent object 703. Theinterface may be within a recess 705 within which the transparent object703 is positioned and/or secured. The recess 705 may have an internaldiameter that exceeds the outside diameter of the transparent object703, thereby allowing expansion of the transparent object 703 within therecess 705. The seal is often subjected to relatively high temperatures(e.g., temperatures in excess of 500° C.), and thus, is typicallyproduced from a material that can withstand relatively hightemperatures. The seal may be produced, in some embodiments, from ametal, a carbon-based material, or a silicone-based material. In someembodiments, the seal is produced from a room-temperature vulcanizing(RTV) silicone elastomer. In some embodiments, the seal is a metallicgasket. Other appropriate seal materials will be apparent to the skilledartisan.

The low pressure fluid chamber 700, in certain embodiments, is designedand constructed to have a maximum allowable working pressure of up toand including 2 atmospheres. As used herein, the term “maximum allowableworking pressure” refers to the maximum pressure a pressure vessel canmaintain, e.g., the maximum pressure that the weakest component of anassembled solar receiver can maintain. Often the maximum allowableworking pressure is determined by conducting a hydrostatic pressuretest. Methods for conducting a hydrostatic pressure test are well knownin the art and will be apparent to the skilled artisan. In oneembodiment, the maximum allowable working pressure of a solar receiveris determined by essentially completely assembling the solar receiver,capping off the fluid inlet(s) and the fluid outlet(s), and pressurizingthe low pressure chamber of the solar receiver with an inert gas, e.g.,air. The low pressure chamber is pressurized, in this embodiment, withthe inert gas at a relatively slow rate, e.g., at a rate in a range of 1psi/second to 5 psi/second, until the low pressure chamber can no longermaintain pressure. The highest pressure maintained during the test isthe maximum allowable working pressure of the solar receiver. In certainembodiments, the weakest component of the solar receiver, such as thesolar receiver depicted in FIG. 7A, is the seal between the transparentobject and the low pressure chamber.

As illustrated by FIGS. 7A and 7B, the transparent object 703 may have avariety of shapes. For example, the transparent object 703 may have aplanar shape (as depicted in FIG. 7A) such as a planar disc or a planarobject having a polygonal cross-section such as a rectangular or squarecross-section. The transparent object may have a relatively slightcurvature inward (as depicted in FIG. 7B) toward the solar absorber. Thetransparent object may have a semi-circular shape, a parabolic shape, anelliptical shape, etc. In some embodiments, a curvature inward towardthe solar absorber serves to minimize tensile stress due to thermalexpansion in the transparent object. Thus, in certain embodiments, thetransparent object has a certain radius of curvature. The transparentobject may, for example, have a radius of curvature of 1 foot to 50feet, 1 foot to 10 feet, 1 foot to 5 feet or 1 foot to 2 feet. Thetransparent object may have a radius of curvature of up to 1 foot, 2feet, 3 feet, 4 feet, 5 feet, 10 feet, 25 feet, 50 feet, or more.

The solar receivers depicted in FIGS. 7A-7C operate at low pressure(e.g., up to and including 2 atmospheres). Because the transparentobject 703 is subjected to relatively small hydrostatic stresses undernormal operation, it may be constructed to have a relatively largediameter and relatively small thickness. In some embodiments, thetransparent object has a diameter in a range 0.5 meter to 5 meters, 2meters to 4 meters or 0.5 meter to 2 meters. In some embodiments, thetransparent object has a diameter of 0.5 meter, 1 meter, 1.2 meters, 1.4meters, 1.6 meters, 1.8 meters, 2 meters, 3 meters, 4 meters, 5 metersor more. In some embodiments, the diameter of a transparent object(e.g., a transparent object that has a certain radius of curvature) isthe diameter of the rim of the transparent object (e.g., the edge of thetransparent object 703 that fits with a recess 705 of the low pressurechamber 700).

The thickness of the transparent object 703 may influence the extent towhich the transparent object 703 absorbs solar radiation, withrelatively thick transparent objects typically absorbing more solarradiation than relatively thin transparent objects. Consequently, thethickness of the transparent object influences the extent to which thetransparent object is subjected to thermal stress during operation ofthe solar receiver. It is therefore often desirable for the transparentobject to have a relatively small thickness, in order to minimizethermal stress. In some embodiments, the thickness of the transparentobject is in a range of 0.25 inch to 4 inches, 0.5 inch to 2 inches, or0.5 inch to 1 inch. In some embodiments, the thickness of thetransparent object is 0.25 inch, 0.5 inch, 1 inch, 1.5 inch, 2 inches, 3inches, 4 inches or more. However, the invention is not limited totransparent objects having these thicknesses. Other thicknesses may besuitable in some cases.

The solar absorber is typically constructed of a material that canwithstand relatively high temperatures, that can absorb incidentradiation and that can readily transfer thermal energy to a workingfluid that is in contact with the absorber. For example, solar absorbersmay be constructed of a metals, stainless steels, ceramics,heat-resistant cast alloys, high temperature metallic materials,refractory materials, thoria-dispersed alloys, graphite, orcarbon-fiber-reinforced carbon-based materials. Appropriate ceramics forsolar absorbers include, for example, glass ceramics, silicon carbide,silicon nitride, and silicon oxide. The solar absorber may have any of avariety of forms. Typically, the solar absorber is designed andconstructed to have a relatively high surface area for contact with aworking fluid. The solar absorber typically comprises a plurality ofchannels or passages through which a working fluid may pass. In passingthrough the fluid channels or passages of the solar absorber, theworking fluid acquires thermal energy through contact with the absorber.The absorber may have a wire mesh, honeycomb or foam configuration, forexample. Often, the solar absorber comprises a black surface coating,covering at least a portion of the absorber surface, to facilitateabsorption of incident solar radiation.

The low pressure solar receivers depicted in FIGS. 7A-7B are fitted witha secondary concentrator 706. The secondary concentrator 706 serves tocollect concentrated solar radiation from a primary concentrator, e.g.,a heliostat field, or other source, and direct that solar radiation intothe opening 708 of the solar receiver. The secondary concentrator 706,in some embodiments, improves the solar collection efficiency of thesolar receiver. The second concentrator 706 is often constructed with aplurality of reflective panels 707, each reflective panel typicallyhaving a reflective surface and a predetermined shape. The plurality ofreflective panels 707 are typically arranged in a configuration thatfacilitates reflection of incident solar radiation toward the receiveropening 708. In some embodiments, the plurality of reflective panels arearranged such that the secondary concentrator has an overall parabolicshape, although other shapes may be suitable. For example, the secondaryconcentrator may have a elliptical shape, a semi-circular shape, ahyperbolic shape, etc.

A cross-section of the secondary concentrator that is parallel with theopening of the receiver may also have a variety of shapes. For example,the cross-section of the secondary concentrator that is parallel withthe opening of the receiver may have a circular shape, an ellipticalshape, a polygonal shape, a rectangular shape, etc.

The size and shape of the secondary concentrator 706 (e.g., the diameterof the outer most portion of the secondary concentrator, the depth ofthe secondary concentrator, etc.) may vary depending on a variety offactors, including, for example, the desired collection efficiency, thesize and arrangement of the primary concentrator(s), the size of theopening of the receiver, the thermal properties of the solar absorber,etc. In some embodiments, the ratio of the depth of the secondaryconcentrator to the diameter of the opening of the receiver is 1, 1.25,1.5, 2, 2.5, 3, 4, 5, or more. In some embodiments, the ratio of thedepth of the secondary concentrator to the diameter of the opening ofthe receiver is in a range of 1 to 1.5, 1 to 2.5, 1 to 3, 1 to 4, or 1to 5. In some embodiments, the ratio of the outer most diameter of thesecondary concentrator to the diameter of the opening of the receiver is1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5.5, 6 or more. In some embodiments, theratio of the depth of the secondary concentrator to the diameter of theopening of the receiver is in a range of 1.5 to 2, 1.5 to 3, 1.5 to 4,1.5 to 5, or 1.5 to 6.

FIG. 7C depicts an exemplary solar receiver having a fluid inlet 702 andfluid outlet 701 that enter and exit, respectively, the solar receiveron different sides of a low pressure fluid chamber. In this embodiment,the solar receiver is connected to a secondary concentrator 706 that hasa rectangularly shaped opening.

FIG. 7D depicts an exemplary solar receiver having a low pressure fluidchamber 716 comprising one or more fluid inlets 715 ₁₋₂ and a fluidoutlet 714, a solar absorber 712, and a regenerator structure 717housing a rotary regenerator matrix 713. In this embodiment, thermalenergy from concentrated solar radiation is directed and concentrated,at least in part, by a secondary concentrator 718 into the low pressurefluid chamber 716 through a transparent object 711 and impinges a solarabsorber 712 thereby heating the solar absorber 712. The solar absorber712 transfers thermal energy to a relatively low temperature workingfluid passing within the low pressure fluid chamber 716, therebycreating a relatively high temperature working fluid. The relativelyhigh temperature fluid leaving the low pressure fluid chamber passesthrough a rotary regenerator matrix 713 and transfers thermal energy tothe rotary regenerator matrix 713.

The rotary regenerator matrix 713, in FIG. 7D, rotates between twofluidically isolated conduits. The first conduit being a flow path forfluid exiting the low pressure fluid chamber 716 of the solar receiver,and the second conduit being a flow path of a second fluid system. Forexample, the rotary regenerator matrix 713 may transfer thermal energyfrom the relatively high temperature fluid leaving the low pressurefluid chamber 716 to a second fluid passing through a conduit adjacentto the receiver that is in fluid communication with the rotaryregenerator matrix. The second fluid may be, for example, a fluid, e.g.,ambient air, entering the compressor of a gas turbine, or a fluid usedto heat a secondary thermal storage material.

FIG. 7E depicts a cross-sectional view of an exemplary solar receiver719 that transfers thermal energy from concentrated solar radiation to alow pressure working fluid. The solar receiver 719 includes an outerhousing 720 defining a first fluid conduit 721 and a fluid inlet 722.The outer housing 720 further defines an aperture 723 for receivingsolar radiation at the front end of the solar receiver 719. Atransparent object 724 is connected to the outer housing 720 through aflange assembly 725 at the aperture 723. The solar receiver 719 alsoincludes an inner housing 726 that defines a second fluid conduit 727and a fluid outlet 728. As described further below, the second fluidconduit 727 is co-axial with the first fluid conduit 721. In addition, asolar absorber 732 is connected to the inner housing 726 at a positionin proximity to the aperture 723. While inlet conduits and outletconduits may be co-axial, it should be appreciated that, in someembodiments, the inlet conduit and outlet conduit are not co-axial.

In an exemplary implementation, concentrated solar radiation is directedto the aperture 723, passes through the transparent object 724 and,after passing through the transparent object 724, and impinges the solarabsorber 732, thereby heating the solar absorber 732. The solar receiver719 defines a fluid path beginning from the fluid inlet 722, traversingforward through the first fluid conduit 721 toward the aperture 723. Thefluid traverses across the inner side of the transparent object 724,passes through a plurality of passages in the solar absorber 732, passesthrough the second fluid conduit 727, and exits the solar receiver 719through the fluid outlet 728.

In certain embodiments, a fluid inlet 722 is at a position in relativeproximity to the transparent object 724 such that fluid enters thereceiver in relative proximity to the transparent object 724. When fluidenters the receiver in this manner it can more readily pass through thesolar absorber in some configurations, such as, for example, when thereceiver has a relatively large diameter.

The fluid inlet 722 may be fluidically connected with a gas turbineexhaust outlet or other working fluid supply conduit, such that arelatively low temperature (e.g., approximately 1100° F.) fluid entersthe solar receiver 719. The solar absorber 732 transfers thermal energyto the relatively low temperature fluid as it travels through theplurality of passages in the solar absorber 732, thereby heating thefluid to a relatively high temperature (e.g., approximately 1800° F.).The fluid outlet 728 may be fluidically connected with a gas turbinecompressor inlet, a heat storage unit, or other downstream componentthat uses the relatively high temperature fluid.

The solar receiver 719 includes a flange assembly 725 for connecting thetransparent object 724 at the aperture 723. The flange assembly 725includes an outer flange 729 that is connected to an inner flange 730.The flange assembly 725 is generally composed of materials that aretolerant to operation at relatively high temperatures (e.g., capable ofoperating at temperatures in the range of 1700 to 2000° F.). Use of ahigh temperature tolerant materials ensures that the flange assembly 725will not fail (e.g., melt or degrade) if concentrated solar radiation(e.g., radiation directed to the receiver from a heliostat field) isimproperly directed such that excess solar radiation impinges on theflange assembly 725. Moreover, in certain embodiments the flangeassembly 725 is composed of materials having thermal properties similarto that of the transparent object 724 to minimize the risk of damage tothe flange assembly 725 or transparent object 724 due to differentialthermal expansion of the components. For example, if the transparentobject 724 is composed of quartz, then it may be advantageous to selectmaterials for the flange assembly 725 that have a similar coefficient ofthermal expansion as quartz. Exemplary materials for the flange assembly725 include, for example, ceramics and other high temperature tolerantmaterials disclosed herein or otherwise known in the art. The outerflange 729 and inner flange 730 are connected, in the illustratedembodiment, by a plurality of bolts positioned around the flangeassembly 725. Flange assembly 725 is also bolted to the outer housing720. In some configurations, bolts connecting the outer flange 729 andinner flange 730 serve to join the entire flange assembly 725 to theouter housing 720. In other configurations, separate bolts join theflange assembly 725 to the outer housing 720. The holes for boltsjoining the flange assembly 725 to the outer housing 720 may be shapedas radial slots to permit differential thermal expansion of the flangeassembly 725 and outer housing 720, and to allow for bolt movementwithin the slots.

The transparent object 724 is connected to the aperture 723 by way of aflange assembly 725. Flexible seals 731 ₁₋₃ are positioned in sealcavities within the flange assembly 725 and provide contact between theflange assembly 725 and transparent object 724 at front, rear andcircumferential surfaces of the transparent object 724. The flexibleseals 731 ₁₋₃ allow for differential thermal expansion (thermal growth)between the flange assembly 725 and the transparent object 724 in theaxial direction (forward and rearward expansion) and radial direction(circumferential expansion). The flexible seals 731 ₁₋₃ prevent directcontact (hard points) between the transparent object 724 and the flangeassembly 725 by providing sealing surfaces with relatively low contactstress. The flexible seals 731 ₁₋₃ provide support for the transparentobject 724 during operation and shipping, and spread the sealing contactload to enhance component life. The flexible seals 731 ₁₋₃ may be madefrom ceramic fiber rope or an equivalent sealing material suitable forhigh temperature operation and for conforming to the dimensions of theseal cavity in the flange assembly 725.

The solar receiver 719 includes a transparent object 724 (which may bereferred to as a window) that is composed quartz silica glass. Thetransparent object 724 may have a curved shaped to contain anddistribute internal pressure, and to tolerate thermal stresses fromdifferential temperature exposure. The curved shape of the transparentobject 724 also limits the formation of destructively high tensilestresses. The transparent object 724 may be designed to accommodateimplementations that give rise to relatively high temperatures at itscenter portion and relatively cooler temperatures at portions inproximity to the flange. Thus, the transparent object 724 may functionin some implementations as a thermal hinge to accommodate thermal growthwithout developing destructively high tensile stresses. The curved (orbowl shape) of the transparent object 724 in the illustrated embodimentalso facilitates, and to an extent directs, flow of a relatively lowtemperature fluid toward and through the solar absorber 732. Therelatively low temperature fluid may also function to cool thetransparent object 724 as it passes over the internal surfaces of thetransparent object 724.

In some embodiments the transparent object is constructed of one piece,e.g., a single solid quartz silica glass window. However, in otherembodiments, the transparent object is constructed of several segmentsthat are fitted together, joined together or butted together. In someembodiments, a transparent object having a diameter in a range of 2meters to 4 meters, or more, is constructed of multiple segments (e.g.,2, 3, 4 or more segments).

The solar receiver 719 is configured and arranged with coaxial(co-annular) first and second fluid conduits, with the first fluidconduit 721 providing a passage for a relatively low temperature fluidand the second fluid conduit 727 providing a passage for a relativelyhigh temperature fluid that has acquired thermal energy from the solarabsorber 732. The solar receiver 719 accommodates a relatively lowtemperature fluid (e.g., approximately 1100° F.) passing through thefirst fluid conduit 721 and relatively high temperature fluid (e.g.,approximately 1800° F.) passing through the second fluid conduit 727with minimal insulation, and minimal thermal losses, in certainembodiments. For example, thermal losses from the second fluid conduit727 are transferred into the first fluid conduit 721 and thus not lostin the overall thermal cycle.

Moreover, the low pressure operation (e.g., operation at up to 1.1 atm)of the solar receiver 719 can allow for the housings that define thefirst and second fluid conduits 721, 727 to be constructed of lightweight and low cost materials, and enable factory fabrication and easyon-site installation. In certain configuration, the outer housing 720 isconstructed of materials suitable for operation at temperatures in arange of 1000° F. to 1200° F. (e.g., approximately 1100° F.). Forexample, the outer housing 720 may be constructed of stainless steel orother similar material. The outer housing 720 may have an externalinsulation to conserve thermal energy and provide a safe workenvironment. The inner housing 726 in a typical configuration isconstructed of materials suitable for operation at temperatures in arange of 1700° F. to 2000° F. (e.g., approximately 1800° F.). Forexample, the inner housing 726 may be constructed of nickel-based superalloy or other similar material. The inner housing 726 may haveinsulation to minimize the extent to which thermal energy is transferredback to the low temperature fluid in the first fluid conduit 721.Because of the low pressure operation conditions of the receiver, insome embodiments, the outer housing 720 and/or inner housing 726 has athickness in a range of 0.001 to 0.1 inch (e.g., approximately 0.05inch).

A bellows 733 is connected between the outer housing 720 and innerhousing 726 and allows for differential thermal expansion between thetwo housings. The bellows 733 is typically constructed of a hightemperature tolerant material such as for example a nickel-based superalloy or other suitable material. The bellows 733 may be connected tothe outer and inner housings 720, 726 by brazing or welding or othersuitable method. It should be appreciated, that the solar receiver 719may be configured with any suitable component to control the axial andradial centering of the two housings and to allow for differentialthermal expansion between the two housings. Vertical support and slipjoints may be included between the housings, for example.

The solar absorber 732 may be constructed of a porous material thatdefines a plurality of passages traversing through the absorber. Thesolar absorber 732 may for example have a honey comb or foam structure.The solar absorber 732 in certain embodiments is constructed of asilicon carbide material. In other embodiments, the solar absorber 732may be constructed of other suitable materials, including any of thematerials disclosed herein for solar absorbers. The solar absorber 732is positioned in a recess 735 defined by the inner housing 726. Theinner housing 726 is fixed to the outer housing 720 at the position ofthe recess 735 by bolts 734 ₁₋₂, which comprise set pins at their endsthat enter into holes in the solar absorber 732 to position the solarabsorber 732.

The overall shape of the solar absorber 732 may be curved. For example,the solar absorber 732 may have radius of curvature that is similar tothat of the transparent object 724. The overall shape of the solarabsorber 732 may alternatively be substantially planar. The solarabsorber 732 may be single solid object or may be arranged as a set ofsegmented components. The solar absorber 732 may be arranged, forexample, as a set of pie-shaped segments in a bowl configuration thatfits within the solar receiver 719. The segmented design allows fordifferential thermal expansion of the different segments and thusaccommodates uneven temperature distributions across the solar absorber.In some configurations temperature distributions across the solarabsorber 732 may be controlled, at least to an extent, by including anorifice plate (e.g., a ceramic orifice plate) at the front end of thesolar absorber. The orifice plate may include a series of orificesconfigured and arranged to facilitate a substantially even distributionof fluid passing into the solar absorber 732 across the entire absorberfluid inlet 722 face. The orifice plate may be retained in the receiveraround its outer rim to control axial and radial movement.

It should be appreciated that the solar receiver 719 may operate atpressures of up to 1.1 atm, up to 1.2 atm, up to 1.3 atm, up to 1.4 atm,up to 1.5 atm, or up to 2 atm. In particular embodiments, the receiveris configured and arranged for operating at pressures in the range ofabove 1 atm to 1.5 atm. In other embodiments, the receiver is configuredand arranged for operating at pressures in the range of above 1 atm to1.2 atm. Moreover, in some embodiments, the solar absorber 732 has aradius of curvature (A) in a range of 50 to 250 inches. In someembodiments, the solar absorber 732 has a radius of curvature (A) in arange of 150 to 200 inches. In some embodiments, the solar absorber 732has a radius of curvature (A) of 170 to 190 inches. Alternatively, thesolar absorber may be substantially planar. In some embodiments, thetransparent object 724 has a radius of curvature (B) in a range of 50 to250 inches. In some embodiments, the transparent object 724 has a radiusof curvature (B) in a range of 150 to 200 inches. In some embodiments,the transparent object 724 has a radius of curvature (B) of 170 to 190inches. In some embodiments, at least a portion of the inner housing 726has an internal diameter (C) in a range of 10 to 50 inches. In someembodiments, at least a portion of the inner housing 726 has an internaldiameter (C) in a range of 20 to 40 inches. In some embodiments, atleast a portion of the inner housing 726 has an internal diameter (C) ina range of 30 to 35 inches. In some embodiments, at least a portion ofthe outer housing 720 has an internal diameter (D) in a range of 25 to65 inches. In some embodiments, at least a portion of the outer housing720 has an internal diameter (D) in a range of 35 to 55 inches. In someembodiments, at least a portion of the outer housing 720 has an internaldiameter (D) in a range of 40 to 50 inches. In some embodiments, thethickness (E) of the transparent object is in a range of about 0.5 inchto about 3 inches. In some embodiments, the thickness (E) of thetransparent object is in a range of about 1 inch to about 2.5 inches. Insome embodiments, the thickness (E) of the transparent object is in arange of about 1.5 inches to about 2 inches. In some embodiments, theflange assembly defines an opening having a diameter (F) in a range of46 inches to 86 inches. In some embodiments, the flange assembly definesan opening having a diameter (F) in a range of 56 inches to 76 inches.In some embodiments, the flange assembly defines an opening having adiameter (F) in a range of 60 inches to 70 inches. In some embodiments,the distance (G) between the inner face of the transparent object 724and the outer face of the solar absorber 732 is in a range of 2 to 12inches. In some embodiments, the distance (G) between the inner face ofthe transparent object 724 and the outer face of the solar absorber 732is in a range of 5 to 8 inches. However, other sizes may be suitable insome configurations.

FIGS. 8A-8C illustrate a secondary concentrator 800 having an integratedfluid cooling system. The secondary concentrator 800 depicted in FIG. 8Aincludes a plurality of connected reflective panels 801. Each of theplurality of reflective panels 801 has a planar shape having a polygonalcross-section. Each reflective panel has an inner reflective surfacethat is positioned to face the inner side of the secondary concentrator800 and an outer surface. The reflective panels 801 are arranged suchthat the secondary concentrator 800 deflects concentrated solarradiation to the opening of the receiver to which the secondaryconcentrator 800 is connected. In some embodiments, the reflectivepanel, e.g., as depicted in FIG. 8A, has a thickness in a range of 0.1inch to 1 inch or 0.1 inch to 0.5 inch.

In the secondary concentrator 800 depicted in FIG. 8A, the reflectivepanels are arranged to form three conical rings. The arrangement ofconical rings is such that the conical ring having the smallest diameteris positioned to the rear of the secondary concentrator 800 and theconical ring having the largest diameter is positioned to the front ofthe secondary concentrator 800. In FIG. 8A the secondary concentrator800 includes two relatively large diameter cooling pipes 802, 803 thatfunction in part to deliver cooling fluid to and from a cooling passagewithin each reflective panel and also to provide a support for arrangingand immobilizing the reflective panels 801 into the predetermined shapethat facilitates concentration of incoming solar radiation andreflection of the incoming concentrated solar radiation to the openingof a low pressure receiver.

FIG. 8B depicts an alternative view of the secondary concentrator 800showing the supply conduit 802, an outlet pipe 803, a smaller diameterpipe 804 in fluid communication with the supply conduit 802 and acooling passage 806 of a reflective panel. The inset at 805 depicts aninlet to a cooling passage 806 of a reflective panel.

FIG. 8C provides an expanded view of the inset 805 in FIG. 8B. As shown,the supply conduit 802 is in fluid communication with cooling passage806 of the reflective panel 801. A series of open slots 810 definepassages through which cooling fluid flows from the supply conduit 802to the cooling passage 806 within the reflective panel 801. The casing808 of the reflective panel 806 and the inner reflective surface 807 arealso shown. In some embodiments, the casing 808 is a metal sheet havinga thickness in a range of 0.01 inch to 0.5 inch or 0.1 inch to 0.5 inch.

Any appropriate cooling fluid may be used to cool a reflective panelhaving a cooling system such as is depicted in FIGS. 8A-8C. In someembodiments, the cooling fluid is a mixture of water and a refrigerant,e.g., ethylene glycol. In some embodiments, the cooling fluid is a 50:50mixture of water and a refrigerant, e.g., ethylene glycol.

Reflective panels of a secondary concentrator may comprise any of avariety of materials. Typically metals, polymers, glass, or combinationsthereof are used. Reflective panels may comprise a metal, such asaluminum, silver, or a combination thereof. Reflective panels maycomprise a non-reflective material having a reflective coating, e.g., areflective silver or reflective aluminum coating. Reflective panels maycomprise a glass substrate, a reflective layer for reflecting solarenergy, and optionally an interference layer (e.g., a layer between theglass and reflective layer comprised of, for example, titanium dioxide).Typically, the reflective panel has at least one surface for reflectingsolar radiation.

FIGS. 9A-9C depict exemplary high pressure receivers that may be used inconjunction with the power generation systems disclosed herein. In theseembodiments, the high pressure receivers include an insulated casing 900having, a working fluid inlet 901, a working fluid outlet 902, and anopening 904 connected to the rear portion of a secondary concentrator906. In some embodiments, such as is depicted in FIGS. 9B-9C, the highpressure receiver includes a transparent object 905, e.g., a window,adjacent to the opening 904 for receiving solar radiation. As in the lowpressure receiver context, the secondary concentrator 906 serves tocollect concentrated solar radiation from a primary concentrator, e.g.,a heliostat field, or other source, and direct that solar radiation intothe opening 904 of the solar receiver.

The high pressure fluid (e.g., fluid at a pressure of above 2atmospheres to 50 atmospheres) passing through the receiver is retainedwithin the high pressure solar absorber 903. The high pressure absorber903, as exemplified in FIGS. 9A-9C, typically comprises a network ofpassages (e.g., a tubular network) for containing a high pressure fluidand directing flow of the high-pressure fluid into and out of thehigh-pressure solar absorber 903.

The high-pressure working fluid enters into the high pressure solarabsorber 903, passes through the network of passages and acquiresthermal energy therein, in part, through contact with the passage walls.The high pressure solar absorber 903 often has a black surface coatingto promote absorption of incident solar radiation. The surface coatingmay be applied using methods well known in the art including, forexample, by chemical vapor deposition (e.g., a pack cementation process,a gas phase coating process, etc.). Moreover, the high pressure absorberis typically constructed from a material that can withstand extremelyhigh temperatures, including, for example, temperatures in excess of1000° C.

The high pressure solar absorber 903 can be designed and constructed inany of a variety of forms. As exemplified in FIGS. 9A and 9B, thetubular network may be a network of tubular coils. As exemplified inFIG. 9C, the tubular network may have a shell and tube-type form. Stillother configurations, such as, for example, a plate type heat exchanger,are envisioned. In some embodiments, the high pressure solar absorbercomprises a tubular network, wherein tubes of the network have adiameter in a range of 0.5 inch to 5 inches in diameter and, in someembodiments, a wall-thickness in a range of 0.1 inch to 1 inch. In someembodiments, the high pressure solar absorber comprises a tubularnetwork, wherein tubes of the network have a diameter in a range of 1inch to 3 inches in diameter and, in some embodiments, a wall-thicknessin a range of 0.1 inch to 0.5 inch.

In some embodiments, the high-pressure solar absorber is constructedfrom a single crystal super alloy. Often the super alloy contains anickel base, chromium at a level sufficient for oxidation resistance(e.g., at a level of about 10%), aluminum and/or titanium (e.g., atlevels of about 2.5% to 5%) for the formation of the strengthening gammaprime phase and refractory metals such as tungsten, molybdenum, tantalumand columbium (e.g., at a level of about 2.5% to 5%) as solid solutionstrengtheners. Typically, nickel base super alloys also contain cobalt(e.g., at a level of about 10%) and carbon (e.g., at a level of about0.1%) which acts as a grain boundary strengthener and forms carbideswhich strengthen the alloy. Boron and zirconium are also often added insmall amounts as grain boundary strengtheners.

Exemplary single crystal super alloys that may be used in theconstruction of high-pressure solar absorber are disclosed in thefollowing United State Patents, the contents of which, relating tosingle crystal super alloys, are incorporated herein by reference intheir entireties: U.S. Pat. Nos. 4,371,404, 4,222,794; 4,514,360;4,643,782; 4,765,850; 4,923,525; 5,047,091; 5,077,004; 5,100,484;5,154,884; 5,366,695; 5,399,313; 5,540,790; and 6,074,602.

Components (e.g., tubes, plate walls, etc.) of the high-pressure solarabsorber may be manufactured by any appropriate techniques, e.g.,extruded or cast. Furthermore, components of the high-pressure solarabsorber may be bonded together using any one of a variety of methodsknown in the art, including, for example, laser welding, electron beamwelding, activated diffusion bonding, etc.

The transparent object 905 provides a barrier for reducing re-radiationlosses, whereby the transparent object 905 allows transmission ofconcentrated solar radiation in the non-infrared range (e.g., in thevisible range) into the solar receiver but does not allow transmissionof radiation in the infrared range. Thus, thermal re-radiation, whichemits in primarily the infrared range from the heated high pressuresolar absorber, is reflected back into in the receiver by thetransparent object 905.

The casing 900 of the receiver is designed and constructed to insulateand provide structural support for the high pressure absorber 903 and tomount the secondary concentrator 906. In the exemplary high-pressurereceivers depicted in FIGS. 9A-9C, the casing 900 operates essentiallyat ambient pressures. As a result, the transparent object, in theseembodiments, is not subjected to substantial hydrostatic pressureinduced stress. Thus, the transparent object can be designed andconstructed to relatively large sizes (e.g., sizes in excess of 5meters, e.g., 5 meters to 10 meters) without concern for hydrostaticpressure induced stress. In some embodiments, the transparent object isconstructed as a combination of multiple transparent objects (e.g., acombination of overlapping transparent objects) to obtain a transparentwindow that functions to prevent re-radiation losses.

Unless otherwise indicated, all pressures described herein refer toabsolute pressures.

The following patents and patent applications are incorporated herein byreference in their entirety for all purposes: U.S. Patent PublicationNo. 2002/0124991, published on Sep. 12, 2002, filed Feb. 1, 2002,entitled “Low Cost High Efficiency Automotive Turbines”; U.S. Pat. No.6,681,557, issued on Jan. 27, 2004, filed Feb. 1, 2002, entitled “LowCost High Efficiency Automotive Turbines”; U.S. Pat. No. 5,259,444,issued on Nov. 9, 1993, filed Nov. 5, 1990, entitled “Heat ExchangerContaining a Component Capable of Discontinuous Movement”; U.S. Pat. No.RE37134, issued on Apr. 17, 2001, filed Mar. 25, 1995, entitled “HeatExchanger Containing a Component Capable of Discontinuous Movement”;U.S. Publication No. 2007/0089283, published on Apr. 26, 2007, filedOct. 17, 2006, entitled “Intermittent Sealing Device and Method”; U.S.Publication No. 2008/0251234, published on Oct. 16, 2008, filed Apr. 16,2007, entitled “Regenerator Wheel Apparatus”; U.S. Publication No.2009/0000761, published on Jan. 1, 2009, filed Jun. 29, 2007. entitled“Regenerative Heat Exchanger with Energy-Storing Drive System”; U.S.Publication No. 2009/0000762, published on Jan. 1, 2009, filed Jun. 29,2007, entitled “Brush-Seal and Matrix for Regenerative Heat Exchangerand Method of Adjusting Same”; and U.S. Publication No. 2006/0054301,published on Mar. 16, 2006, filed Dec. 16, 2004, entitled “Variable AreaMass or Area and Mass Species Transfer Device and Method.”

The following examples are intended to illustrate certain embodiments ofthe present invention, but do not exemplify the full scope of theinvention.

EXAMPLE 1

This example describes a concentrated solar power generation system inwhich a pressurized solar receiver is used. FIG. 10A includes aschematic diagram of such a system. In this example, compressed air fromthe compressor is fed to the solar receiver and heated whilepressurized. The heated effluent from the solar receiver is thenexpanded through the gas turbine to produce power. The exhaust from thegas turbine is used to pre-heat the pressurized gas from the compressorbefore it is transported to the solar receiver.

EXAMPLE 2

This example describes a concentrated solar power generation system inwhich a thermal storage system is incorporated. FIG. 10B includes aschematic diagram of the exemplary system. Air is used as the fluid inthis system. The temperatures of process streams are indicated in thefigure. In this example, ambient air at 59° F. is supplied to thecompressor, where it is compressed and heated to a temperature of 1700°F. in a heat exchange system comprising one, two or more recuperatorheat exchangers. The 1700° F. air is passed through a turbine togenerate power, which produces an exhaust stream at 1100° F. The turbineexhaust and a portion of the heat exchange system exhaust aretransported to the solar receiver, where they are heated to 1800° F. Aportion of the solar receiver-heated air can be transported to thethermal storage system (similar to a cowper stove) for storage. Thebalance of the solar receiver-heated air is passed to the two-stage heatexchanger, where it is used to heat the compressed air upstream. Itshould be noted that other components, such as a startup combustorand/or a thermal recovery unit, could also be included in this example.

EXAMPLE 3

This example describes a concentrated solar power generation system inwhich thermal storage is not included. FIG. 10C includes a schematicdiagram of the exemplary system. Air is used as the fluid in thissystem, and the temperatures of process streams are indicated in thefigure. Similar to the system described in Example 1, ambient air at 59°F. is supplied to the compressor, where it is compressed and heated to atemperature of 1700° F. in a heat exchange system comprising one, two ormore recuperator heat exchangers. The 1700° F. air is passed through aturbine to generate power, which produces an exhaust stream at 1100° F.The turbine exhaust (and optionally, a portion of the heat exchangesystem exhaust) is transported to the solar receiver, where they areheated to 1800° F. The solar receiver-heated air is then passed to thetwo-stage heat exchanger, where it is used to heat upstream compressedair.

EXAMPLE 4

This example describes a concentrated solar power generation system inwhich one, two or more thermal storage units and one, two or more rotaryheat exchangers are used within the system. FIG. 10D includes aschematic diagram of the exemplary system. In this example, rather thanusing a two-stage heat exchanger to heat the compressed air from thecompressor, a single rotary heat exchanger is used. A cross-sectionalview of the rotary heat exchanger is shown in the upper-left corner ofthe figure.

FIG. 10D also includes two thermal storage units. The units can beconfigured such that none, one, or both of the units is able to acceptheated air from the solar receiver and/or provide heated air to therotary regenerator for heating the compressed air stream to the turbine.

EXAMPLE 5

This example describes a concentrated solar power generation system inwhich two or more compressors and two or more turbines are used toproduce energy. FIG. 10E includes a schematic diagram of the exemplarysystem. As in the previous examples, stream temperatures are provided inthe figure.

EXAMPLE 6

This example describes a concentrated solar power generation system inwhich a high-pressure solar receiver and a low-pressure solar receiverare used in a single system. FIG. 10F includes a schematic diagram ofthe exemplary system. As in the previous examples, stream temperaturesare provided in the figure. The layout of the components in this exampleis similar to the layout described in association with FIG. 10E.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,and/or methods, if such features, systems, articles, materials, and/ormethods are not mutually inconsistent, is included within the scope ofthe present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, inone embodiment, to A without B (optionally including elements other thanB); in another embodiment, to B without A (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is: 1-111. (canceled)
 112. The solar receiver of claim264, wherein the maximum allowable working pressure of the fluid chamberis equal to or less than 2 atm. 113-115. (canceled)
 116. The solarreceiver of claim 264, wherein the fluid chamber defines a recess withinwhich an outer rim of the transparent object expandably fits, the recessbeing adjacent to the opening.
 117. The solar receiver of claim 116,wherein the flexible seal is positioned between the outer rim of thetransparent object and an interface defined by the recess on the fluidchamber.
 118. The solar receiver of claim 264, wherein the flexible sealelement is a room temperature vulcanizing (RTV) silicone or ceramicfiber rope.
 119. (canceled)
 120. The solar receiver of claim 263,wherein the solar absorber is a material selected from a groupconsisting of metals, stainless steels, ceramics, heat-resistant castalloys, high-temperature metallic materials, refractory materials,thoria-dispersed alloys, graphite, and carbon-fiber-reinforcedcarbon-based materials.
 121. The solar receiver of claim 263, whereinthe solar absorber is a wire mesh or constructed of a ceramic. 122-125.(canceled)
 126. The solar receiver of claim 263, wherein the solarabsorber has a honeycomb configuration.
 127. The solar receiver of claim263, wherein the solar absorber comprises a black surface coating. 128.The solar receiver of claim 263, wherein the solar absorber comprises aplurality of segments. 129-131. (canceled)
 132. The solar receiver ofclaim 263, wherein the transparent object of the solar receiver has asubstantially planar shape. 133-262. (canceled)
 263. A solar receivercomprising: a fluid chamber comprising a fluid inlet, a fluid outlet,and an opening for receiving concentrated solar radiation; a solarabsorber housed within the fluid chamber; and a transparent object thatdefines at least a portion of a wall of the fluid chamber; whereinconcentrated solar radiation received through the opening passes throughthe transparent object into the fluid chamber and impinges upon thesolar absorber; and wherein the fluid chamber is constructed andarranged to have a maximum working pressure not exceeding 2 atmospheresas determined by a hydrostatic pressure test comprising: assembling thesolar receiver; capping off the fluid inlet and the fluid outlet; andpressurizing the fluid chamber until the fluid chamber can no longermaintain pressure; wherein a highest pressure maintained during the testwithout leakage is the maximum working pressure of the solar receiver.264. A solar receiver comprising: a fluid chamber comprising a fluidinlet, a fluid outlet, and an opening for receiving concentrated solarradiation; a solar absorber housed within the fluid chamber; and atransparent object forming a window of the fluid chamber, wherein aflexible seal provides a sealing connection between an interface on thefluid chamber and the transparent object; wherein concentrated solarradiation received through the opening passes through the transparentobject into the fluid chamber and impinges upon the solar absorber. 265.The solar receiver of claim 264, wherein the solar absorber isconstructed of one or more materials chosen from a ceramic,heat-resistant cast alloy, high-temperature metal, refractory material,thoria-dispersed alloy, graphite, and/or a carbon-fiber-reinforcedcarbon-based material.
 266. The solar receiver of claim 264, wherein thesolar absorber is a wire mesh or is constructed of a ceramic.
 267. Thesolar receiver of claim 264, wherein the solar absorber has a honeycombconfiguration.
 268. The solar receiver of claim 264, wherein the solarabsorber comprises a black surface coating.
 269. The solar receiver ofclaim 264, wherein the solar absorber comprises a plurality of segments.270. The solar receiver of claim 264, wherein the transparent object ofthe solar receiver has a substantially planar shape.
 271. A solarreceiver comprising: a fluid chamber comprising a fluid inlet, a fluidoutlet, and an opening for receiving concentrated solar radiation; asolar absorber housed within the fluid chamber; a transparent objectthat defines at least a portion of a wall of the fluid chamber; and aflange assembly for connecting the transparent object at the openingcapable of operating at temperatures in the range of 1700 to 2000° F.,wherein concentrated solar radiation received through the opening passesthrough the transparent object into the fluid chamber and impinges uponthe solar absorber.
 272. The solar receiver of claim 271, wherein thesolar absorber is constructed of one or more materials chosen from aceramic, heat-resistant cast alloy, high-temperature metal, refractorymaterial, thoria-dispersed alloy, graphite, and/or acarbon-fiber-reinforced carbon-based material.
 273. The solar receiverof claim 271, wherein the solar absorber is a wire mesh or isconstructed of a ceramic.
 274. The solar receiver of claim 271, whereinthe solar absorber has a honeycomb configuration.
 275. The solarreceiver of claim 271, wherein the solar absorber comprises a blacksurface coating.
 276. The solar receiver of claim 267, wherein the solarabsorber comprises a plurality of segments.
 277. The solar receiver ofclaim 271, wherein the transparent object of the solar receiver has asubstantially planar shape.
 278. The solar receiver of claim 271,wherein the maximum allowable working pressure of the fluid chamber isequal to or less than 2 atm.